runtime: set runtime.GOROOT value at build time

In Go 1.17 the gc toolchain changed to set runtime.GOROOT in cmd/link
(previously it was runtime/internal/sys.GOROOT).  Do the same in libgo.

Reviewed-on: https://go-review.googlesource.com/c/gofrontend/+/351313

gotools/:
	* Makefile.am (check-runtime): Add goroot.go to --extrafiles.
	* Makefile.in: Regenerate.
diff --git a/gcc/go/gofrontend/MERGE b/gcc/go/gofrontend/MERGE
index e2abd5f..edfbe46 100644
--- a/gcc/go/gofrontend/MERGE
+++ b/gcc/go/gofrontend/MERGE
@@ -1,4 +1,4 @@
-850235e4b974b9c5c2d7a1f9860583bd07f2a45c
+e3bfc0889237a5bb8aa7ae30e1cff14f90a5f941
 
 The first line of this file holds the git revision number of the last
 merge done from the gofrontend repository.
diff --git a/gotools/Makefile.am b/gotools/Makefile.am
index 6576fe7..199899b 100644
--- a/gotools/Makefile.am
+++ b/gotools/Makefile.am
@@ -245,14 +245,14 @@
 	export LD_LIBRARY_PATH; \
 	GOARCH=`$(abs_builddir)/go$(EXEEXT) env GOARCH`; \
 	GOOS=`$(abs_builddir)/go$(EXEEXT) env GOOS`; \
-	files=`$(SHELL) $(libgosrcdir)/../match.sh --goarch=$${GOARCH} --goos=$${GOOS} --srcdir=$(libgosrcdir)/runtime --extrafiles="$(libgodir)/runtime_linknames.go $(libgodir)/runtime_sysinfo.go $(libgodir)/sigtab.go" --tag=libffi`; \
+	files=`$(SHELL) $(libgosrcdir)/../match.sh --goarch=$${GOARCH} --goos=$${GOOS} --srcdir=$(libgosrcdir)/runtime --extrafiles="$(libgodir)/runtime_linknames.go $(libgodir)/runtime_sysinfo.go $(libgodir)/sigtab.go $(libgodir)/goroot.go" --tag=libffi`; \
 	echo "$(ECHO_ENV) GC='$(abs_builddir)/check-gccgo -fgo-compiling-runtime' GOARCH=$${GOARCH} GOOS=$${GOOS} $(SHELL) $(libgosrcdir)/../testsuite/gotest --goarch=$${GOARCH} --goos=$${GOOS} --basedir=$(libgosrcdir)/.. --srcdir=$(libgosrcdir)/runtime --pkgpath=runtime --pkgfiles='$${files}' $(GOTESTFLAGS) -test.timeout=$(GOTOOLS_TEST_TIMEOUT)s -test.v" > runtime-testlog
 	$(CHECK_ENV) \
 	GC="$${GCCGO} -fgo-compiling-runtime"; \
 	export GC; \
 	GOARCH=`$(abs_builddir)/go$(EXEEXT) env GOARCH`; \
 	GOOS=`$(abs_builddir)/go$(EXEEXT) env GOOS`; \
-	files=`$(SHELL) $(libgosrcdir)/../match.sh --goarch=$${GOARCH} --goos=$${GOOS} --srcdir=$(libgosrcdir)/runtime --extrafiles="$(libgodir)/runtime_linknames.go $(libgodir)/runtime_sysinfo.go $(libgodir)/sigtab.go" --tag=libffi`; \
+	files=`$(SHELL) $(libgosrcdir)/../match.sh --goarch=$${GOARCH} --goos=$${GOOS} --srcdir=$(libgosrcdir)/runtime --extrafiles="$(libgodir)/runtime_linknames.go $(libgodir)/runtime_sysinfo.go $(libgodir)/sigtab.go $(libgodir)/goroot.go" --tag=libffi`; \
 	$(SHELL) $(libgosrcdir)/../testsuite/gotest --goarch=$${GOARCH} --goos=$${GOOS} --basedir=$(libgosrcdir)/.. --srcdir=$(libgosrcdir)/runtime --pkgpath=runtime --pkgfiles="$${files}" $(GOTESTFLAGS) -test.timeout=$(GOTOOLS_TEST_TIMEOUT)s -test.v >> runtime-testlog 2>&1 || echo "--- $${fl}: go test runtime (0.00s)" >> runtime-testlog
 	grep '^--- ' runtime-testlog | sed -e 's/^--- \(.*\) ([^)]*)$$/\1/' | sort -k 2
 
diff --git a/gotools/Makefile.in b/gotools/Makefile.in
index c442686..e2c30bf 100644
--- a/gotools/Makefile.in
+++ b/gotools/Makefile.in
@@ -703,8 +703,8 @@
 maintainer-clean-generic:
 	@echo "This command is intended for maintainers to use"
 	@echo "it deletes files that may require special tools to rebuild."
-@NATIVE_FALSE@uninstall-local:
 @NATIVE_FALSE@install-exec-local:
+@NATIVE_FALSE@uninstall-local:
 clean: clean-am
 
 clean-am: clean-binPROGRAMS clean-generic clean-noinstPROGRAMS \
@@ -916,14 +916,14 @@
 @NATIVE_TRUE@	export LD_LIBRARY_PATH; \
 @NATIVE_TRUE@	GOARCH=`$(abs_builddir)/go$(EXEEXT) env GOARCH`; \
 @NATIVE_TRUE@	GOOS=`$(abs_builddir)/go$(EXEEXT) env GOOS`; \
-@NATIVE_TRUE@	files=`$(SHELL) $(libgosrcdir)/../match.sh --goarch=$${GOARCH} --goos=$${GOOS} --srcdir=$(libgosrcdir)/runtime --extrafiles="$(libgodir)/runtime_linknames.go $(libgodir)/runtime_sysinfo.go $(libgodir)/sigtab.go" --tag=libffi`; \
+@NATIVE_TRUE@	files=`$(SHELL) $(libgosrcdir)/../match.sh --goarch=$${GOARCH} --goos=$${GOOS} --srcdir=$(libgosrcdir)/runtime --extrafiles="$(libgodir)/runtime_linknames.go $(libgodir)/runtime_sysinfo.go $(libgodir)/sigtab.go $(libgodir)/goroot.go" --tag=libffi`; \
 @NATIVE_TRUE@	echo "$(ECHO_ENV) GC='$(abs_builddir)/check-gccgo -fgo-compiling-runtime' GOARCH=$${GOARCH} GOOS=$${GOOS} $(SHELL) $(libgosrcdir)/../testsuite/gotest --goarch=$${GOARCH} --goos=$${GOOS} --basedir=$(libgosrcdir)/.. --srcdir=$(libgosrcdir)/runtime --pkgpath=runtime --pkgfiles='$${files}' $(GOTESTFLAGS) -test.timeout=$(GOTOOLS_TEST_TIMEOUT)s -test.v" > runtime-testlog
 @NATIVE_TRUE@	$(CHECK_ENV) \
 @NATIVE_TRUE@	GC="$${GCCGO} -fgo-compiling-runtime"; \
 @NATIVE_TRUE@	export GC; \
 @NATIVE_TRUE@	GOARCH=`$(abs_builddir)/go$(EXEEXT) env GOARCH`; \
 @NATIVE_TRUE@	GOOS=`$(abs_builddir)/go$(EXEEXT) env GOOS`; \
-@NATIVE_TRUE@	files=`$(SHELL) $(libgosrcdir)/../match.sh --goarch=$${GOARCH} --goos=$${GOOS} --srcdir=$(libgosrcdir)/runtime --extrafiles="$(libgodir)/runtime_linknames.go $(libgodir)/runtime_sysinfo.go $(libgodir)/sigtab.go" --tag=libffi`; \
+@NATIVE_TRUE@	files=`$(SHELL) $(libgosrcdir)/../match.sh --goarch=$${GOARCH} --goos=$${GOOS} --srcdir=$(libgosrcdir)/runtime --extrafiles="$(libgodir)/runtime_linknames.go $(libgodir)/runtime_sysinfo.go $(libgodir)/sigtab.go $(libgodir)/goroot.go" --tag=libffi`; \
 @NATIVE_TRUE@	$(SHELL) $(libgosrcdir)/../testsuite/gotest --goarch=$${GOARCH} --goos=$${GOOS} --basedir=$(libgosrcdir)/.. --srcdir=$(libgosrcdir)/runtime --pkgpath=runtime --pkgfiles="$${files}" $(GOTESTFLAGS) -test.timeout=$(GOTOOLS_TEST_TIMEOUT)s -test.v >> runtime-testlog 2>&1 || echo "--- $${fl}: go test runtime (0.00s)" >> runtime-testlog
 @NATIVE_TRUE@	grep '^--- ' runtime-testlog | sed -e 's/^--- \(.*\) ([^)]*)$$/\1/' | sort -k 2
 
diff --git a/libgo/Makefile.am b/libgo/Makefile.am
index 92fedcf..5c377a3 100644
--- a/libgo/Makefile.am
+++ b/libgo/Makefile.am
@@ -545,6 +545,14 @@
 	$(SHELL) $(srcdir)/mvifdiff.sh gcpugen.go.tmp gcpugen.go
 	$(STAMP) $@
 
+goroot.go: s-goroot; @true
+s-goroot: Makefile
+	rm -f goroot.go.tmp
+	echo "package runtime" > goroot.go.tmp
+	echo 'var defaultGOROOT = `$(prefix)`' >> goroot.go.tmp
+	$(SHELL) $(srcdir)/mvifdiff.sh goroot.go.tmp goroot.go
+	$(STAMP) $@
+
 buildcfg.go: s-buildcfg; @true
 s-buildcfg: Makefile
 	rm -f buildcfg.go.tmp
@@ -1005,7 +1013,8 @@
 math_check_GOCFLAGS = $(MATH_FLAG)
 
 # Add generated files to the runtime package.
-extra_go_files_runtime = runtime_linknames.go runtime_sysinfo.go sigtab.go
+extra_go_files_runtime = \
+	runtime_linknames.go runtime_sysinfo.go sigtab.go goroot.go
 runtime.lo.dep: $(extra_go_files_runtime)
 
 # Add generated files to the syscall package.
diff --git a/libgo/Makefile.in b/libgo/Makefile.in
index 3b2bdf9..1240b16 100644
--- a/libgo/Makefile.in
+++ b/libgo/Makefile.in
@@ -1098,7 +1098,9 @@
 math_check_GOCFLAGS = $(MATH_FLAG)
 
 # Add generated files to the runtime package.
-extra_go_files_runtime = runtime_linknames.go runtime_sysinfo.go sigtab.go
+extra_go_files_runtime = \
+	runtime_linknames.go runtime_sysinfo.go sigtab.go goroot.go
+
 
 # Add generated files to the syscall package.
 extra_go_files_syscall = \
@@ -2752,6 +2754,14 @@
 	$(SHELL) $(srcdir)/mvifdiff.sh gcpugen.go.tmp gcpugen.go
 	$(STAMP) $@
 
+goroot.go: s-goroot; @true
+s-goroot: Makefile
+	rm -f goroot.go.tmp
+	echo "package runtime" > goroot.go.tmp
+	echo 'var defaultGOROOT = `$(prefix)`' >> goroot.go.tmp
+	$(SHELL) $(srcdir)/mvifdiff.sh goroot.go.tmp goroot.go
+	$(STAMP) $@
+
 buildcfg.go: s-buildcfg; @true
 s-buildcfg: Makefile
 	rm -f buildcfg.go.tmp
diff --git a/libgo/go/runtime/extern.go b/libgo/go/runtime/extern.go
index 0d7f357..6bd612f 100644
--- a/libgo/go/runtime/extern.go
+++ b/libgo/go/runtime/extern.go
@@ -211,8 +211,6 @@
 // program counter adjustment.
 func Callers(skip int, pc []uintptr) int
 
-var defaultGOROOT string // set by cmd/link
-
 // GOROOT returns the root of the Go tree. It uses the
 // GOROOT environment variable, if set at process start,
 // or else the root used during the Go build.