[gdb/testsuite] Fix gdb.cp/cplusfuncs.exp with check-read1

When running check-read1, we run into:
...
FAIL: gdb.cp/cplusfuncs.exp: info function for "operator=(" (timeout)
...

Fix this by using using gdb_test_lines in info_func_regexp.

Tested on x86_64-linux.

gdb/testsuite/ChangeLog:

2021-06-10  Tom de Vries  <tdevries@suse.de>

	* gdb.cp/cplusfuncs.exp (info_func_regexp): Use gdb_test_lines.
diff --git a/gdb/testsuite/ChangeLog b/gdb/testsuite/ChangeLog
index 39aa648..5e74a6a 100644
--- a/gdb/testsuite/ChangeLog
+++ b/gdb/testsuite/ChangeLog
@@ -1,3 +1,7 @@
+2021-06-10  Tom de Vries  <tdevries@suse.de>
+
+	* gdb.cp/cplusfuncs.exp (info_func_regexp): Use gdb_test_lines.
+
 2021-06-09  Tom Tromey  <tromey@adacore.com>
 
 	* README (Example): Update read1 example.
diff --git a/gdb/testsuite/gdb.cp/cplusfuncs.exp b/gdb/testsuite/gdb.cp/cplusfuncs.exp
index f1c2ff4..19be8ab 100644
--- a/gdb/testsuite/gdb.cp/cplusfuncs.exp
+++ b/gdb/testsuite/gdb.cp/cplusfuncs.exp
@@ -287,13 +287,16 @@
 #
 
 proc info_func_regexp { name demangled } {
-    global gdb_prompt
+    global srcfile decimal
 
     regsub {\\\(void\\\)} $demangled {\(\)} demangled
 
-    gdb_test "info function $name" \
-	"File .*:\t(class|)${demangled}.*" \
-	"info function for \"$name\""
+    set file_re "File .*[string_to_regexp $srcfile]:"
+
+    gdb_test_lines "info function $name" "info function for \"$name\"" \
+	[list \
+	     "$file_re" \
+	     "$decimal:\t(class|)${demangled}.*"]
 }
 
 #