CI: Backport GitHub Actions from 3.x branch

Ensures that we have a configuration that is currently usable.

Some changes for the `3.2` branch as it's unmaintained:
- No cache
- No artifacts upload
- Uses clang-format 10
- No JavaScript linting

.github/workflows/linux_builds.yml

@@ -1,13 +1,12 @@
 name: 🐧 Linux Builds
 on: [push, pull_request]
 
-# Global Cache Settings
+# Global Settings
 env:
-  GODOT_BASE_BRANCH: 3.2
-  SCONS_CACHE_LIMIT: 4096
+  SCONSFLAGS: platform=linuxbsd verbose=yes warnings=all werror=yes debug_symbols=no --jobs=2
 
 jobs:
-  linux-editor:
+  linux-editor-mono:
     runs-on: "ubuntu-20.04"
     name: Editor w/ Mono (target=release_debug, tools=yes)
 
@@ -17,27 +16,16 @@ jobs:
       # Azure repositories are not reliable, we need to prevent azure giving us packages.
       - name: Make apt sources.list use the default Ubuntu repositories
         run: |
+          sudo rm -f /etc/apt/sources.list.d/*
           sudo cp -f misc/ci/sources.list /etc/apt/sources.list
           sudo apt-get update
 
       # Install all packages (except scons)
       - name: Configure dependencies
         run: |
-          sudo apt-get install build-essential pkg-config libx11-dev libxcursor-dev \
+          sudo apt-get install build-essential pkg-config libx11-dev libxcursor-dev xvfb \
             libxinerama-dev libgl1-mesa-dev libglu-dev libasound2-dev libpulse-dev libudev-dev libxi-dev libxrandr-dev yasm
 
-      # Upload cache on completion and check it out now
-      - name: Load .scons_cache directory
-        id: linux-editor-cache
-        uses: actions/cache@v2
-        with:
-          path: ${{github.workspace}}/.scons_cache/
-          key: ${{github.job}}-${{env.GODOT_BASE_BRANCH}}-${{github.ref}}-${{github.sha}}
-          restore-keys: |
-            ${{github.job}}-${{env.GODOT_BASE_BRANCH}}-${{github.ref}}-${{github.sha}}
-            ${{github.job}}-${{env.GODOT_BASE_BRANCH}}-${{github.ref}}
-            ${{github.job}}-${{env.GODOT_BASE_BRANCH}}
-
       # Use python 3.x release (works cross platform; best to keep self contained in it's own step)
       - name: Set up Python 3.x
         uses: actions/setup-python@v2
@@ -57,12 +45,13 @@ jobs:
 
       # We should always be explicit with our flags usage here since it's gonna be sure to always set those flags
       - name: Compilation
-        env:
-          SCONS_CACHE: ${{github.workspace}}/.scons_cache/
         run: |
-          scons -j2 verbose=yes warnings=all werror=yes platform=x11 tools=yes target=release_debug module_mono_enabled=yes mono_glue=no
+          scons tools=yes target=release_debug module_mono_enabled=yes mono_glue=no
+          xvfb-run ./bin/godot.x11.opt.tools.64.mono --generate-mono-glue modules/mono/glue || true
+          scons tools=yes target=release_debug module_mono_enabled=yes mono_glue=yes
+          ls -l bin/
 
-  linux-template:
+  linux-template-mono:
     runs-on: "ubuntu-20.04"
     name: Template w/ Mono (target=release, tools=no)
 
@@ -72,6 +61,7 @@ jobs:
       # Azure repositories are not reliable, we need to prevent azure giving us packages.
       - name: Make apt sources.list use the default Ubuntu repositories
         run: |
+          sudo rm -f /etc/apt/sources.list.d/*
           sudo cp -f misc/ci/sources.list /etc/apt/sources.list
           sudo apt-get update
 
@@ -81,18 +71,6 @@ jobs:
           sudo apt-get install build-essential pkg-config libx11-dev libxcursor-dev \
             libxinerama-dev libgl1-mesa-dev libglu-dev libasound2-dev libpulse-dev libudev-dev libxi-dev libxrandr-dev yasm
 
-      # Upload cache on completion and check it out now
-      - name: Load .scons_cache directory
-        id: linux-template-cache
-        uses: actions/cache@v2
-        with:
-          path: ${{github.workspace}}/.scons_cache/
-          key: ${{github.job}}-${{env.GODOT_BASE_BRANCH}}-${{github.ref}}-${{github.sha}}
-          restore-keys: |
-            ${{github.job}}-${{env.GODOT_BASE_BRANCH}}-${{github.ref}}-${{github.sha}}
-            ${{github.job}}-${{env.GODOT_BASE_BRANCH}}-${{github.ref}}
-            ${{github.job}}-${{env.GODOT_BASE_BRANCH}}
-
       # Use python 3.x release (works cross platform)
       - name: Set up Python 3.x
         uses: actions/setup-python@v2
@@ -111,7 +89,6 @@ jobs:
           scons --version
 
       - name: Compilation
-        env:
-          SCONS_CACHE: ${{github.workspace}}/.scons_cache/
         run: |
-          scons -j2 verbose=yes warnings=all werror=yes platform=x11 target=release tools=no module_mono_enabled=yes mono_glue=no
+          scons target=release tools=no module_mono_enabled=yes mono_glue=no
+          ls -l bin/