Makefile: don't pass -mstrict-align if not supported

Support for that option will be added in LLVM 18:
https://github.com/llvm/llvm-project/commit/23ce5368409c760f3dd49d0f17f34772b0b869d8



Clang 17.0.6, however, will error when passed the
`-mstrict-align` flag.
We should only use the flag if it is supported.

Signed-off-by: Kalle Wachsmuth <kalle.wachsmuth@gmail.com>
Reviewed-by: Anup Patel <anup@brainfault.org>
Reviewed-by: Xiang W <wxjstz@126.com>