Fix ident tests by Enabling ident output for X86 Darwin.

The c-c++-common tests fail (or XPASS depending on which) on Darwin
because it doesn't currently emit .ident marker.  For X86 Darwin, this
is a trivial oversight; the assembler supports the directive.  We can
therefore use the default target hook there.

2018-12-23  Iain Sandoe  <iain@sandoe.co.uk>

        * config/i386/darwin.h (TARGET_ASM_OUTPUT_IDENT): New.

From-SVN: r267372

gcc/ChangeLog

 2018-12-23  Iain Sandoe  <iain@sandoe.co.uk>
 
+	* config/i386/darwin.h (TARGET_ASM_OUTPUT_IDENT): New.
+
+2018-12-23  Iain Sandoe  <iain@sandoe.co.uk>
+
 	* collect2.c (maybe_run_lto_and_relink): Don’t say we have a temp file
 	unless we actually did some LTO.
 	(has_lto_section, is_lto_object_file): New.

gcc/config/i386/darwin.h

@@ -219,6 +219,11 @@ extern int darwin_emit_branch_islands;
         }				\
     } while (0)
 
+/* Darwin x86 assemblers support the .ident directive.  */
+
+#undef TARGET_ASM_OUTPUT_IDENT
+#define TARGET_ASM_OUTPUT_IDENT default_asm_output_ident_directive
+
 /* Darwin profiling -- call mcount.  */
 #undef FUNCTION_PROFILER
 #define FUNCTION_PROFILER(FILE, LABELNO)				\