libsanitizer: Only build libhwasan when targeting AArch64

libsanitizer:  Only build libhwasan when targeting AArch64

Though the library has limited support for x86, we don't have any
support for generating code targeting x86 so there is no point building
for that target.

Ensure we build for AArch64 but not for AArch64 ilp32.

libsanitizer/ChangeLog:

	* Makefile.am: Condition Build hwasan directory.
	* Makefile.in: Regenerate.
	* configure: Regenerate.
	* configure.ac: Set HWASAN_SUPPORTED based on target
	architecture.
	* configure.tgt: Likewise.