check-uapi: honor ${CROSS_COMPILE} setting

When ${CROSS_COMPILE} is set, but ${CC} is not set, the logic in
check-uapi.sh is different from the top-level Makefile, which defaults
to using the cross gcc. This leads to using the native gcc instead of the
cross version, resulting in unexpected false-positive and false-negative
output.

Use the same logic here that we use in Kbuild for consistency.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Thomas Weißschuh <linux@weissschuh.net>
Acked-by: Nathan Chancellor <nathan@kernel.org>
Link: https://patch.msgid.link/20260306163309.2015837-3-arnd@kernel.org
Signed-off-by: Nicolas Schier <nsc@kernel.org>

scripts/check-uapi.sh

@@ -33,9 +33,10 @@ Options:
     -v             Verbose operation (print more information about each header being checked).
 
 Environmental args:
-    ABIDIFF  Custom path to abidiff binary
-    CC       C compiler (default is "gcc")
-    ARCH     Target architecture for the UAPI check (default is host arch)
+    ABIDIFF        Custom path to abidiff binary
+    CROSS_COMPILE  Toolchain prefix for compiler
+    CC             C compiler (default is "\${CROSS_COMPILE}gcc")
+    ARCH           Target architecture for the UAPI check (default is host arch)
 
 Exit codes:
     $SUCCESS) Success
@@ -198,7 +199,7 @@ do_compile() {
 run_make_headers_install() {
 	local -r ref="$1"
 	local -r install_dir="$(get_header_tree "$ref")"
-	make -j "$MAX_THREADS" ARCH="$ARCH" INSTALL_HDR_PATH="$install_dir" \
+	make -j "$MAX_THREADS" CROSS_COMPILE="${CROSS_COMPILE}" ARCH="$ARCH" INSTALL_HDR_PATH="$install_dir" \
 		headers_install > /dev/null
 }
 
@@ -407,7 +408,7 @@ min_version_is_satisfied() {
 # Make sure we have the tools we need and the arguments make sense
 check_deps() {
 	ABIDIFF="${ABIDIFF:-abidiff}"
-	CC="${CC:-gcc}"
+	CC="${CC:-${CROSS_COMPILE}gcc}"
 	ARCH="${ARCH:-$(uname -m)}"
 	if [ "$ARCH" = "x86_64" ]; then
 		ARCH="x86"