migrate OS independent jobs from macOS to linux runners

.github/workflows/make_files_tree.yml

@@ -11,19 +11,25 @@ on:
 jobs:
   fetch_new_content:
     name: Make files tree
-    runs-on: macos-10.15
+    runs-on: ${{matrix.os}}
     continue-on-error: true
     timeout-minutes: 10
 
     strategy:
       fail-fast: false
       matrix:
-        mode: [
-          "web",
-          "web_res",
-          "server",
-          "client"
-        ]
+        include:
+          - mode: web
+            os: ubuntu-20.04
+
+          - mode: web_res
+            os: ubuntu-20.04
+
+          - mode: server
+            os: ubuntu-20.04
+
+          - mode: client
+            os: macos-10.15
 
     steps: