sim: erc32: drop old configure target

There is no configure script in here anymore to regenerate.
diff --git a/sim/erc32/Makefile.in b/sim/erc32/Makefile.in
index 613f9fa..7d91519 100644
--- a/sim/erc32/Makefile.in
+++ b/sim/erc32/Makefile.in
@@ -52,11 +52,3 @@
 
 clean-sis:
 	rm -f sis
-
-configure:
-	@echo "Rebuilding configure..."
-	if [ x"${srcdir}" = x"@srcdir@" ] ; then \
-	  srcdir=. ; export srcdir ; \
-	else true ; fi ; \
-	(cd $${srcdir}; autoconf --localdir=../common)
-