Update blank.yml

.github/workflows/blank.yml

@@ -33,8 +33,7 @@ jobs:
           ./gradlew publishToMavenLocal
           ./gradlew -Pskiko.native.enabled=true publishToMavenLocal
    linux:
-    # Shall be ubuntu-16.04, but clang is incompatible
-    runs-on: ubuntu-20.04
+    runs-on: ubuntu-16.04
     
     # Steps represent a sequence of tasks that will be executed as part of the job
     steps:
@@ -48,6 +47,17 @@ jobs:
       - shell: bash
         run: |
           cd ./skiko
+          # TODO: simplify installation of compilers.
+          sudo apt-get update -y
+          sudo apt-get install build-essential software-properties-common -y
+          sudo add-apt-repository ppa:ubuntu-toolchain-r/test -y
+          sudo apt-get update -y
+          sudo apt-get install build-essential software-properties-common -y
+          sudo apt-get update
+          sudo apt-get install gcc-9 g++-9 -y
+          sudo update-alternatives --install /usr/bin/gcc gcc /usr/bin/gcc-9 60 --slave /usr/bin/g++ g++ /usr/bin/g++-9
+          sudo update-alternatives --config gcc 
+          sudo apt-get install ninja-build fontconfig libfontconfig1-dev libglu1-mesa-dev zip -y          
           ./gradlew publishToMavenLocal
    windows:
     runs-on: windows-2019