Fix x86 ld testsuite fails with glibc < 2.28

Fix x86 ld testsuite fails with glibc < 2.28

	* testsuite/ld-elf/linux-x86.exp: Build tests when non-native.
	(check_pr25749b): Add optional args.  Set expected pass file
	from args.  Run -1b and -2a tests with passall.out.
	* testsuite/ld-elf/passall.out: New file.
	* testsuite/ld-elf/pr25749-1.c: Adjust to pass with older glibc.
	* testsuite/ld-elf/pr25749-2.c: Likewise.
	* testsuite/lib/ld-lib.exp (run_ld_link_exec_tests): Use
	regexp_diff to compare expected output from running binary.