hardening: Disable GCC randstruct for COMPILE_TEST

There is a GCC crash bug in the randstruct for latest GCC versions that
is being tickled by landlock[1]. Temporarily disable GCC randstruct for
COMPILE_TEST builds to unbreak CI systems for the coming -rc2. This can
be restored once the bug is fixed.

Suggested-by: Mark Brown <broonie@kernel.org>
Link: https://lore.kernel.org/all/20250407-kbuild-disable-gcc-plugins-v1-1-5d46ae583f5e@kernel.org/ [1]
Acked-by: Mark Brown <broonie@kernel.org>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Link: https://lore.kernel.org/r/20250409151154.work.872-kees@kernel.org
Signed-off-by: Kees Cook <kees@kernel.org>

Author: kees

security/Kconfig.hardening

@@ -344,7 +344,7 @@ config CC_HAS_RANDSTRUCT
 
 choice
 	prompt "Randomize layout of sensitive kernel structures"
-	default RANDSTRUCT_FULL if COMPILE_TEST && (GCC_PLUGINS || CC_HAS_RANDSTRUCT)
+	default RANDSTRUCT_FULL if COMPILE_TEST && CC_HAS_RANDSTRUCT
 	default RANDSTRUCT_NONE
 	help
 	  If you enable this, the layouts of structures that are entirely