configure.ac: Treat a --with-headers option without argument the same as the default (i.e.

	* configure.ac: Treat a --with-headers option without argument
	the same as the default (i.e. consult sys-include directory).
	* configure: Regenerate.

From-SVN: r236825

gcc/ChangeLog

+2016-05-27  Ulrich Weigand  <uweigand@de.ibm.com>
+
+	* configure.ac: Treat a --with-headers option without argument
+	the same as the default (i.e. consult sys-include directory).
+	* configure: Regenerate.
+
 2016-05-27  Kyrylo Tkachov  <kyrylo.tkachov@arm.com>
 
 	* config/aarch64/aarch64.c (aarch64_fusion_enabled_p): New function.

gcc/configure

@@ -12289,7 +12289,7 @@ elif test "x$TARGET_SYSTEM_ROOT" != x; then
 fi
 
 if test x$host != x$target || test "x$TARGET_SYSTEM_ROOT" != x; then
-  if test "x$with_headers" != x; then
+  if test "x$with_headers" != x && test "x$with_headers" != xyes; then
     target_header_dir=$with_headers
   elif test "x$with_sysroot" = x; then
     target_header_dir="${test_exec_prefix}/${target_noncanonical}/sys-include"

gcc/configure.ac

@@ -2035,7 +2035,7 @@ elif test "x$TARGET_SYSTEM_ROOT" != x; then
 fi
 
 if test x$host != x$target || test "x$TARGET_SYSTEM_ROOT" != x; then
-  if test "x$with_headers" != x; then
+  if test "x$with_headers" != x && test "x$with_headers" != xyes; then
     target_header_dir=$with_headers
   elif test "x$with_sysroot" = x; then
     target_header_dir="${test_exec_prefix}/${target_noncanonical}/sys-include"