testsuite, Darwin: Allow two undefined symbols in the 99849 test.

Darwin's linker defaults to requiring all symbols to be resolved at static-
link time.  This test creates a shared object with two undefined symbols,
allow them for Darwin.

gcc/testsuite/ChangeLog:

	* gcc.dg/lto/pr99849_0.c: Allo baz and qux to be undefined at
	static-link time.

Signed-off-by: Iain Sandoe <iain@sandoe.co.uk>