[PATCH] LoongArch: Allow using --with-arch=native if host CPU is LoongArch

[Xi Ruoyao <xry111@xry111.site>]

If the host triple and the target triple are different but the host is
LoongArch, in some cases --with-arch=native can be useful.  For example,
if we are bootstrapping a loongarch64-linux-musl toolchain on a
Glibc-based system and we don't intend to use the toolchain on other
machines, we can use

    ../gcc/configure --{build,host}=loongarch64-linux-gnu \
                     --target=loongarch64-linux-musl --with-arch=native

Relax the check in config.gcc to allow such configurations.

gcc/ChangeLog:

	* config.gcc [target=loongarch*-*-*, with_arch=native]: Allow
	building cross compiler if the host CPU is LoongArch.
---

Tested on x86_64-linux-gnu (building a cross compiler targeting
LoongArch --with-arch=native still rejected) and loongarch64-linux-gnu
(building a cross compiler targeting loongarch64-linux-musl allowed).
Ok for trunk?

 gcc/config.gcc | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/gcc/config.gcc b/gcc/config.gcc
index 1446eb2b3ca..146bca22a38 100644
--- a/gcc/config.gcc
+++ b/gcc/config.gcc
@@ -4939,10 +4939,13 @@ case "${target}" in
 		case ${with_arch} in
 		"" | loongarch64 | la464) ;; # OK, append here.
 		native)
-			if test x${host} != x${target}; then
+			case ${host} in
+			loongarch*) ;; # OK
+			*)
 				echo "--with-arch=native is illegal for cross-compiler." 1>&2
 				exit 1
-			fi
+				;;
+			esac
 			;;
 		"")
 			echo "Please set a default value for \${with_arch}" \
-- 
2.41.0