Pull x86 build updates from Ingo Molnar:
"More Clang support related fixes"
* 'x86-build-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
x86/build: Use cc-option to validate stack alignment parameter
x86/build: Fix stack alignment for CLang
x86/build: Drop unused mflags-y