Fix unexpected failures in GAS testsuite for ARM VxWorks target.

Fix unexpected failures in GAS testsuite for ARM VxWorks target.

	PR 19456
	* testsuite/gas/arm/weakdef-1.d: Skip for VxWorks.
	* testsuite/gas/arm/blx-bl-convert.d
	* testsuite/gas/arm/plt-1.d: Likewise.
	* testsuite/gas/arm/reloc-bad.d: Likewise.
	* testsuite/gas/arm/thumb-w-good.d: Likewise.
	* testsuite/gas/arm/thumb2_pool.d: Likewise.
	* testsuite/gas/arm/ldconst.d: Adjust so that it works with VxWorks
	* testsuite/gas/arm/tls_vxworks.d: Update expected output.