jit: fix ICE with GCC_JIT_BOOL_OPTION_SELFCHECK_GC since r278084 (PR jit/92483)

Since r278084 (part of the params refactoring), most of libgccjit's
test suite has been ICEing.

The root cause is that jit-playback.c injects params to its fake_args
here:

  /* Aggressively garbage-collect, to shake out bugs: */
  if (get_bool_option (GCC_JIT_BOOL_OPTION_SELFCHECK_GC))
    {
      ADD_ARG ("--param");
      ADD_ARG ("ggc-min-expand=0");
      ADD_ARG ("--param");
      ADD_ARG ("ggc-min-heapsize=0");
    }

(building a vec of char * where the char * are allocated using xstrdup)

and r278084 added this logic to decode_cmdline_options_to_array:

964	      /* Interpret "--param" "key=name" as "--param=key=name".  */
965	      const char *needle = "--param";
966	      if (i + 1 < argc && strcmp (opt, needle) == 0)
967		{
968		  const char *replacement
969		    = opts_concat (needle, "=", argv[i + 1], NULL);
970		  argv[++i] = replacement;
971		}

Note that at line 970 it manipulates the argv in-place, inserting a
new option allocated with opts_concat, which uses opts_obstack
(itself initialized from toplev::main).

jit-playback.c cleans up its fake arguments using "free", at which
point we have a free of the middle of an obstack and an ICE.

This patch fixes the issue by using the new syntax for the params.

Fixes all 60 FAILs in jit.sum, restoring the number of PASS results
from 2033 to 10469.

gcc/jit/ChangeLog:
	PR jit/92483
	* jit-playback.c (gcc::jit::playback::context::make_fake_args):
	Update GCC_JIT_BOOL_OPTION_SELFCHECK_GC for new --param syntax.

From-SVN: r278515

gcc/jit/ChangeLog

+2019-11-20  David Malcolm  <dmalcolm@redhat.com>
+
+	PR jit/92483
+	* jit-playback.c (gcc::jit::playback::context::make_fake_args):
+	Update GCC_JIT_BOOL_OPTION_SELFCHECK_GC for new --param syntax.
+
 2019-08-13  Richard Sandiford  <richard.sandiford@arm.com>
 
 	PR middle-end/91421

gcc/jit/jit-playback.c

@@ -2273,10 +2273,8 @@ make_fake_args (vec <char *> *argvec,
   /* Aggressively garbage-collect, to shake out bugs: */
   if (get_bool_option (GCC_JIT_BOOL_OPTION_SELFCHECK_GC))
     {
-      ADD_ARG ("--param");
-      ADD_ARG ("ggc-min-expand=0");
-      ADD_ARG ("--param");
-      ADD_ARG ("ggc-min-heapsize=0");
+      ADD_ARG ("--param=ggc-min-expand=0");
+      ADD_ARG ("--param=ggc-min-heapsize=0");
     }
 
   if (get_bool_option (GCC_JIT_BOOL_OPTION_DUMP_EVERYTHING))