fips: fix build on !Linux

Commit 0f66998f makes -enable-fips conditional on Linux hosts but then uses it
unconditionally in vl.c.

Fix this by moving the fips handling to os-posix.c and adding a condition.

Cc: Paul Moore <pmoore@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>

os-posix.c

@@ -188,6 +188,11 @@ void os_parse_cmd_args(int index, const char *optarg)
     case QEMU_OPTION_daemonize:
         daemonize = 1;
         break;
+#if defined(CONFIG_LINUX)
+    case QEMU_OPTION_enablefips:
+        fips_set_state(true);
+        break;
+#endif
     }
     return;
 }

vl.c

@@ -3199,9 +3199,6 @@ int main(int argc, char **argv, char **envp)
             case QEMU_OPTION_qtest_log:
                 qtest_log = optarg;
                 break;
-            case QEMU_OPTION_enablefips:
-                fips_set_state(true);
-                break;
             default:
                 os_parse_cmd_args(popt->index, optarg);
             }