testsuite,Darwin,PPC: Adjust darwin-abi-12.c for common section use.

This test explicitly tests for code generation that expects a
common section.

gcc/testsuite/ChangeLog:

2020-02-02  Iain Sandoe  <iain@sandoe.co.uk>

* gcc.target/powerpc/darwin-abi-12.c: Add '-fcommon' to the
options.

gcc/testsuite/ChangeLog

+2020-02-02  Iain Sandoe  <iain@sandoe.co.uk>
+
+	* gcc.target/powerpc/darwin-abi-12.c: Add '-fcommon' to the
+	options.
+
 2020-02-02  Vladimir Makarov  <vmakarov@redhat.com>
 
 	PR rtl-optimization/91333

gcc/testsuite/gcc.target/powerpc/darwin-abi-12.c

 /* { dg-do compile { target powerpc*-*-darwin* } } */
+/* This test explicitly checks for output that expects common.  */
+/* { dg-additional-options "-fcommon" { target powerpc*-*-darwin* } } */
 /* { dg-final { scan-assembler ".comm\[\t \]_x,12,2" } } */
 /* { dg-final { scan-assembler-not ".space 7" } } */
 /* PR 23071 */