[testsuite, Darwin] Fix failing darwin-version-1.c.

[testsuite, Darwin] Fix failing darwin-version-1.c.

Recent platform linkers will no longer accept linking for a target
OS version less than 10.4.  Recent SDKs no longer have the libgcc_s
shims used for 10.4 and 10.5.  So we need to adjust tests that expect
these.

gcc/testsuite/ChangeLog:

2020-01-05  Iain Sandoe  <iain@sandoe.co.uk>

	* gcc.dg/darwin-version-1.c: Adjust test to use different
	options for Darwin4-9 and Darwin10+.

From-SVN: r279888