Add 2 testcases for PR ld/22269

Add 2 testcases for PR ld/22269

Since undefined weak symbols in static PIE are always resolved to 0 at
run-time, linker should resolve them as 0 at link-time, regardless of
whether "-z dynamic-undefined-weak" is used.  "-z dynamic-undefined-weak"
only makes undefined weak symbols dynamic, but doesn't change undefined
weak symbol resolution in static PIE at link-time.  These tests currently
pass on x86, but fails on many other targets.

The framework to resolve weak symbols in static PE at link-time is
posted at

https://sourceware.org/ml/binutils/2017-10/msg00087.html

which requires users/hjl/check_relocs branch to call check_relocs after
opening all inputs.  I will submit backend patches for failling targets
after merging users/hjl/check_relocs branch next.

	* PR ld/22269
	* testsuite/ld-elf/pr22269.s: New file.
	* testsuite/ld-elf/pr22269a.d: Likewise.
	* testsuite/ld-elf/pr22269b.d: Likewise.