Add dockerfile for building linux-x86-64 binaries

.github/workflows/linux-x86-64.yml

@@ -0,0 +1,20 @@
+name: linux-x86-64 building.
+on:
+  push:
+    branches:
+      - master
+jobs:
+  build-binary:
+    runs-on: ubuntu-18.04
+    steps:
+    - uses: actions/checkout@v2
+    - name: build binary
+      run: |
+        docker build . -f Dockerfile.pc  -t sdl2_playground-builder-pc
+        docker run -it --rm -v ${PWD}:/project sdl2_playground-builder-pc bash -c "cd .. && bash filelist.sh"
+        docker run -it --rm -v ${PWD}:/project sdl2_playground-builder-pc cmake ..
+        docker run -it --rm -v ${PWD}:/project sdl2_playground-builder-pc make
+    - uses: actions/upload-artifact@master
+      with:
+       name: linux-x86-64-shared binary
+       path: "./cmake-build/SDL2_Playground"

.github/workflows/pc-win.yml

@@ -14,5 +14,5 @@ jobs:
         docker run --rm -v ${PWD}:/project sdl2_playground-builder-pc-win make -f Makefile.pc-win
     - uses: actions/upload-artifact@master
       with:
-       name: binary
+       name: windows-shared binary
        path: "*.exe"

Dockerfile.pc

@@ -0,0 +1,12 @@
+FROM debian:sid-slim
+RUN DEBIAN_FRONTEND="noninteractive"
+RUN echo 'debconf debconf/frontend select Noninteractive' | debconf-set-selections
+RUN apt-get update && \
+    apt-get install -y --no-install-recommends apt-utils ca-certificates && \
+    apt-get install -y --no-install-recommends build-essential make git && \
+    apt-get install -y --no-install-recommends cmake && \
+    apt-get install -y --no-install-recommends libsdl2-ttf-dev libsdl2-image-dev libsdl2-mixer-dev libsdl2-dev && \
+    apt-get clean && \
+    rm -rf /var/lib/apt/lists/*
+RUN mkdir -p /project/cmake-build
+WORKDIR /project/cmake-build

README.md

@@ -9,6 +9,23 @@ bash ./filelist.sh
 mkdir build && cd build && cmake .. && make
 ```
 
+Via docker: 
+```
+# Build the docker image
+docker build . -f .\Dockerfile.pc  -t sdl2_playground-builder-pc
+
+# Build filelist.h
+docker run -it --rm -v ${PWD}:/project sdl2_playground-builder-pc bash -c "cd .. && bash filelist.sh"
+
+# Generate the makefile
+docker run -it --rm -v ${PWD}:/project sdl2_playground-builder-pc cmake ..
+
+# build!
+docker run -it --rm -v ${PWD}:/project sdl2_playground-builder-pc make
+
+# The result will be in ${PWD}/cmake-build
+```
+
 ## Windows binaries
 
 ### Windows with devkitPros version of msys2