lto: Set resolution to LDPR_PREVAILING_DEF for regular common symbol

Since size or alignment of common symbol may be overridden by another
common symbol, set symbol resolution to LDPR_PREVAILING_DEF, instead of
LDPR_RESOLVED_EXEC, for common symbol in regular object when seeing an
undefined or common symbol from an IR object.

	PR ld/34570
	* plugin.c (get_symbols): Set resolution to LDPR_PREVAILING_DEF
	for common symbol in regular object.
	* testsuite/ld-plugin/pr34570a.c: New file.
	* testsuite/ld-plugin/pr34570a.d: Likewise.
	* testsuite/ld-plugin/pr34570b.c: Likewise.
	* testsuite/ld-plugin/pr34570b.d: Likewise.
	* testsuite/ld-plugin/pr34570c.c: Likewise.
	* testsuite/ld-plugin/pr34570c.d: Likewise.

Signed-off-by: H.J. Lu <hjl.tools@gmail.com>