elf: Add is_standard_elf

elf: Add is_standard_elf

PR ld/31289 tests failed for fr30-elf, frv-elf, ft32-elf, iq2000-elf,
mn10200-elf, ms1-elf and msp430-elf targets:

FAIL: ld-elf/fatal-warnings-2a
FAIL: ld-elf/fatal-warnings-2b
FAIL: ld-elf/fatal-warnings-3a
FAIL: ld-elf/fatal-warnings-3b
FAIL: ld-elf/fatal-warnings-4a
FAIL: ld-elf/fatal-warnings-4b

even though PR ld/31289 targets xfail for [is_generic] targets.  These
targets not only don't use the generic_link_hash_table linker, but also
don't use the standard ELF emulation.  Add is_standard_elf for ELF
targets which use the standard ELF emulation and replace [is_generic]
with ![is_standard_elf] in PR ld/31289 tests.

binutils/

	PR ld/31289
	* testsuite/lib/binutils-common.exp (is_standard_elf): New.

ld/

	PR ld/31289
	* testsuite/lib/binutils-common.exp (is_generic): Return 1 for
	fr30-*-*, frv-*-elf, ft32-*-*, iq2000-*-*, mn10200-*-*,
	moxie-*-moxiebox*, msp430-*-* and mt-*-*.
	* testsuite/ld-elf/fatal-warnings-2a.d: Replace [is_generic]
	with ![is_standard_elf].
	* testsuite/ld-elf/fatal-warnings-2b.d: Likewise.
	* testsuite/ld-elf/fatal-warnings-3a.d: Likewise.
	* testsuite/ld-elf/fatal-warnings-3b.d: Likewise.
	* testsuite/ld-elf/fatal-warnings-4a.d: Likewise.
	* testsuite/ld-elf/fatal-warnings-4b.d: Likewise.