debug/111409 - don't generate COMDAT macro sections for split DWARF

Split DWARF files aren't processed by the linker, so DW_MACRO_import
offsets aren't relocated and the .debug_macro.dwo sections aren't
deduplicated and merged.  There's no clear way for this to work for
split DWARF, so disable it.

gcc/ChangeLog:

	PR debug/111409
	* dwarf2out.cc (output_macinfo): Don't call optimize_macinfo_range if
	dwarf_split_debug_info.

gcc/testsuite/ChangeLog:

	PR debug/111409
	* gcc.dg/pr111409.c: New test.

gcc/dwarf2out.cc

@@ -29247,6 +29247,7 @@ output_macinfo (const char *debug_line_label, bool early_lto_debug)
 	case DW_MACINFO_define:
 	case DW_MACINFO_undef:
 	  if ((!dwarf_strict || dwarf_version >= 5)
+	      && !dwarf_split_debug_info
 	      && HAVE_COMDAT_GROUP
 	      && vec_safe_length (files) != 1
 	      && i > 0

gcc/testsuite/gcc.dg/pr111409.c

@@ -0,0 +1,7 @@
+/* { dg-do compile } */
+/* { dg-skip-if "split DWARF unsupported" { *-*-darwin* } } */
+/* { dg-options "-gsplit-dwarf -g3 -dA" } */
+/* { dg-final { scan-assembler-times {.section\s+.debug_macro} 1 } } */
+/* { dg-final { scan-assembler-not {.byte\s+0x7\s*#\s*Import} } } */
+
+#define foo 1