Fix Fortran STOP.

The minimal libgfortran setup was created for NVPTX, but will also be used by
AMD GCN.

This patch simply removes an assumption that NVPTX is the only user.
Specifically, NVPTX exit is broken, but AMD GCN exit works just fine.

2018-09-12  Andrew Stubbs  <ams@codesourcery.com>

	libgfortran/
	* runtime/minimal.c (exit): Only work around nvptx bugs on nvptx.

From-SVN: r264238

libgfortran/ChangeLog

+2018-09-12  Andrew Stubbs  <ams@codesourcery.com>
+
+	* runtime/minimal.c (exit): Only work around nvptx bugs on nvptx.
+
 2018-09-07  Janne Blomqvist  <jb@gcc.gnu.org>
 
 	* runtime/environ.c (init_unsigned_integer): Remove.

libgfortran/runtime/minimal.c

@@ -197,10 +197,12 @@ sys_abort (void)
 #define st_printf printf
 #undef estr_write
 #define estr_write printf
+#if __nvptx__
 /* Map "exit" to "abort"; see PR85463 '[nvptx] "exit" in offloaded region
    doesn't terminate process'.  */
 #undef exit
 #define exit(...) do { abort (); } while (0)
+#endif
 #undef exit_error
 #define exit_error(...) do { abort (); } while (0)