x86: Skip ISA check for always_inline in system headers

x86: Skip ISA check for always_inline in system headers

For always_inline in system headers, we don't know if caller's ISAs are
compatible with callee's ISAs until much later.  Skip ISA check for
always_inline in system headers if caller has target attribute.

gcc/

	PR target/98209
	PR target/99744
	* config/i386/i386.c (ix86_can_inline_p): Don't check ISA for
	always_inline in system headers.

gcc/testsuite/

	PR target/98209
	PR target/99744
	* gcc.target/i386/pr98209.c: New test.
	* gcc.target/i386/pr99744-1.c: Likewise.
	* gcc.target/i386/pr99744-2.c: Likewise.