Put spec in included file

.gitlab-ci-unix.yml

+spec:
+  inputs:
+    os:
+    platform:
+    tagname:
+    cross_platform:
+      default: 'no'
+    build_flags:
+      default: 'RELEASE=1'
+    no_javascript:
+      default: 'no'
+---
 ".$[[ inputs.os ]]":
   extends: .rules
   tags: 

.gitlab-ci.yml

-spec:
-  inputs:
-    os:
-      default: ''
-    platform:
-      default: ''
-    tagname:
-      default: ''
-    cross_platform:
-      default: 'no'
-    build_flags:
-      default: 'RELEASE=1'
-    no_javascript:
-      default: 'no'
----
 .rules:
   rules:
     - changes: