sim: testsuite: support exit 77 for unsupported tests

Exit status 77 is common (including the autotools world) to indicate
"skip this test".  Add support for mapping that to "unsupported" as
that's the closest in the dejagnu world.

sim/testsuite/ChangeLog

@@ -1,3 +1,8 @@
+2021-04-08  Mike Frysinger  <vapier@gentoo.org>
+
+	* lib/sim-defs.exp (run_sim_test): Set status to unsupported if
+	$return_code is 77.
+
 2021-04-08  Mike Frysinger  <vapier@gentoo.org>
 
 	* lib/sim-defs.exp (run_sim_test): Return if sim_tool_path does not

sim/testsuite/lib/sim-defs.exp

@@ -402,7 +402,9 @@ proc run_sim_test { name requested_machs } {
 	set output [lindex $result 1]
 
 	set status fail
-	if { $return_code == $opts(status) } {
+	if { $return_code == 77 } {
+	    set status unsupported
+	} elseif { $return_code == $opts(status) } {
 	    set status pass
 	}