Fix Fortran compiler detection

- Test with '-x' operator to ensure file is executable.
- 'break' is not a valid Perl keyword.

f_check

@@ -32,11 +32,12 @@ if ($compiler eq "") {
 	      "pgf95", "pgf90", "pgf77",
               "ifort");
     
+OUTER:
     foreach $lists (@lists) {
         foreach $path (@path) {
-            if (-f $path . "/" . $lists) {
+            if (-x $path . "/" . $lists) {
                 $compiler = $lists;
-                break;
+                last OUTER;
             }
         }
     }