LLVM 9+ no longer pretends to be gcc 4.2.1

Index: configure.ac
--- configure.ac.orig
+++ configure.ac
@@ -193,7 +193,7 @@ gcc4=no
 if test "$GCC" = yes && test "$ICC" = no ; then
     case `$CC -dumpversion 2>/dev/null` in
 	""|2.*|3.*) ;;
-	4.*) gcc4=yes ;;
+	*) gcc4=yes ;;
     esac
     case "$CC" in
 	*clang) gcc4=yes ;;
