x86: Don't enable UINTR in 32-bit mode

x86: Don't enable UINTR in 32-bit mode

UINTR is available only in 64-bit mode.  Since the codegen target is
unknown when the the gcc driver is processing -march=native, to properly
handle UINTR for -march=native:

1. Pass "arch [32|64]" and "tune [32|64]" to host_detect_local_cpu to
indicate 32-bit and 64-bit codegen.
2. Change ix86_option_override_internal to enable UINTR only in 64-bit
mode for -march=CPU when PTA_CPU includes PTA_UINTR.

gcc/

	PR target/101395
	* config/i386/driver-i386.c (host_detect_local_cpu): Check
	"arch [32|64]" and "tune [32|64]" for 32-bit and 64-bit codegen.
	Enable UINTR only for 64-bit codegen.
	* config/i386/i386-options.c
	(ix86_option_override_internal::DEF_PTA): Skip PTA_UINTR if not
	in 64-bit mode.
	* config/i386/i386.h (ARCH_ARG): New.
	(CC1_CPU_SPEC): Pass "[arch|tune] 32" for 32-bit codegen and
	"[arch|tune] 64" for 64-bit codegen.

gcc/testsuite/

	PR target/101395
	* gcc.target/i386/pr101395-1.c: New test.
	* gcc.target/i386/pr101395-2.c: Likewise.
	* gcc.target/i386/pr101395-3.c: Likewise.