Fix problem where gold does not create base version for executables.

gold/
	PR gold/23268
	* dynobj.cc (Versions::Versions): Change init for needs_base_version_.
	(Versions::record_version): Add verdefs for both shared objects and
	executables.
	(Versions::add_def): Likewise for base version.
	(Versions::add_need): Don't add base version for executables.
	(Versions::version_index): Look up version for both shared objects and
	executables.
	* testsuite/Makefile.am (ver_test_14): New test case.
	* testsuite/Makefile.in: Regenerate.
	* testsuite/ver_test_14.script: New version script.
	* testsuite/ver_test_14.sh: New test script.