Update workflow

.github/workflows/main.yml

-name: Pt.1 Build with GCC
+name: Pt.2 Build with Emscripten
 # Controls when the action will run. Triggers the workflow on push or pull request
 # events but only for the master branch
 on:
   push:
-    branches: [ n4.3.1-p1 ]
+    branches: [ n4.3.1-p2 ]
   pull_request:
-    branches: [ n4.3.1-p1 ]
+    branches: [ n4.3.1-p2 ]
+
+env:
+  EM_VERSION: 1.39.18
+  EM_CACHE_FOLDER: 'emsdk-cache'
 
 jobs:
   linux-build_with_docker:
@@ -16,25 +20,32 @@ jobs:
         shell: bash
         run: |
           bash build-with-docker.sh
-      - uses: actions/upload-artifact@master
-        with:
-          name: ffmpeg-linux
-          path: ffmpeg
+      # - uses: actions/upload-artifact@master
+      #   with:
+      #     name: ffmpeg-linux
+      #     path: ffmpeg
   macos-build:
     runs-on: macos-latest
     steps:
       - uses: actions/checkout@v2
+      - name: Setup cache
+        id: cache-system-libraries
+        uses: actions/cache@v2
+        with:
+          path: ${{env.EM_CACHE_FOLDER}}
+          key: ${{env.EM_VERSION}}-${{ runner.os }}
+      - uses: mymindstorm/setup-emsdk@v6
+        with:
+          version: ${{env.EM_VERSION}}
+          actions-cache-folder: ${{env.EM_CACHE_FOLDER}}
       - name: Build FFMpeg
         shell: bash
         run: |
-          # Make sure to use gcc-8 instead of the default gcc
-          shopt -s expand_aliases
-          alias gcc='gcc-8'
           bash build.sh
-      - uses: actions/upload-artifact@master
-        with:
-          name: ffmpeg-macos
-          path: ffmpeg
+      # - uses: actions/upload-artifact@master
+      #   with:
+      #     name: ffmpeg-macos
+      #     path: ffmpeg
   # Not working with error messsage:
   #   C:\ProgramData\Chocolatey\lib\mingw\tools\install\mingw64\x86_64-w64-mingw32\bin\ar.exe: libavfilter/vsink_null: No such file or directory
   # windows-build:

build-with-docker.sh

 #!/bin/bash -x
 
+EM_VERSION=1.39.18-upstream
 FLAGS=""
 # Attach TTY only when available, this is for running in Gihub Actions
 if [ -t 1 ]; then FLAGS="-it"; fi
 
-docker pull gcc:8
+docker pull trzeci/emscripten:$EM_VERSION
 docker run $FLAGS \
-  -v $PWD:/usr/src \
-  gcc:8 \
-  sh -c 'cd /usr/src && bash ./build.sh'
+  -v $PWD:/src \
+  trzeci/emscripten:$EM_VERSION \
+  sh -c 'bash ./build.sh'

build.sh

 #!/bin/bash
 
-./configure --disable-x86asm
-make -j
+emcc -v