Update CI to use GCC 11 on Linux

.github/workflows/build.yml

@@ -199,6 +199,10 @@ jobs:
           # Most dependencies are already installed in the Docker image. Uncomment the following lines if you need more
           # apt-get update && apt-get install ...
 
+          # Install GCC 11 and make it default (necessary for JUCE 8) (https://forum.juce.com/t/juce-8-linux-issue-with-harfbuzz/61970/3)
+          apt-get update && apt-get install g++-11 gcc-11
+          update-alternatives --install /usr/bin/gcc gcc /usr/bin/gcc-11 100 --slave /usr/bin/g++ g++ /usr/bin/g++-11 --slave /usr/bin/gcov gcov /usr/bin/gcov-11
+
           cd $GITHUB_WORKSPACE
           wget "https://github.com/AppImage/AppImageKit/releases/download/13/appimagetool-x86_64.AppImage"
           chmod a+x appimagetool-x86_64.AppImage
@@ -315,6 +319,10 @@ jobs:
             apt-get install -qyf libcurl3-gnutls libfreetype6-dev libx11-dev libxinerama-dev libxrandr-dev libxcursor-dev libxcomposite-dev mesa-common-dev libasound2-dev freeglut3-dev libcurl4-gnutls-dev libasound2-dev libjack-dev libbluetooth-dev libgtk-3-dev libwebkit2gtk-4.0-dev libsdl2-dev libusb-1.0-0-dev libhidapi-dev ladspa-sdk libssl-dev
             apt-get install -qy curl
 
+            # Install GCC 11 and make it default (necessary for JUCE 8) (https://forum.juce.com/t/juce-8-linux-issue-with-harfbuzz/61970/3)
+            apt-get install g++-11 gcc-11
+            update-alternatives --install /usr/bin/gcc gcc /usr/bin/gcc-11 100 --slave /usr/bin/g++ g++ /usr/bin/g++-11 --slave /usr/bin/gcov gcov /usr/bin/gcov-11
+
             cd Builds/${{ matrix.buildFolder }}
             make -j2 CONFIG=${{ matrix.buildConfig }}