Build inside container

Mostly do it in order to be able to upload the entire /usr/local which
is empty inside the minimal container but contains plenty of other stuff
in the default GitHub Actions environment -- this is much simpler than
uploading just the files installed by "make install" or installing them
in some other directory.

Also separate 32- and 64-bit builds.

.github/workflows/build_msw_xml_libs.yml

@@ -7,25 +7,38 @@ jobs:
   build-xml-libs:
     name: Build XML binaries
     runs-on: ubuntu-latest
+    container: debian:stable-slim
+
+    strategy:
+      fail-fast: false
+      matrix:
+        include:
+          - name: 32 Bits
+            host: i686-w64-mingw32
+          - name: 64 Bits
+            host: x86_64-w64-mingw32
+
+    env:
+      HOST: ${{ matrix.host }}
+
     steps:
       - name: Checkout
         uses: actions/checkout@v2
 
-      - name: Install Compiler
-        run: |
-          sudo apt-get update -qq
-          sudo apt-get install -qq --no-install-recommends g++-mingw-w64-i686 g++-mingw-w64-x86-64
-
-      - name: Build 32-bit Libraries
+      - name: Install Tools
         run: |
-          HOST=i686-w64-mingw32 ./scripts/install_deps.sh
+          apt-get update -qq
+          arch=`echo $HOST | sed -e 's/-w64-mingw32$//;s/_/-/'`
+          apt-get install -qq --no-install-recommends g++-mingw-w64-$arch make pkg-config wget
 
-      - name: Build 64-bit Libraries
+      - name: Build
         run: |
-          HOST=x86_64-w64-mingw32 ./scripts/install_deps.sh
+          # sudo doesn't work and is not necessary inside a container, so don't use it.
+          SUDO=env ./scripts/install_deps.sh
 
       - name: Upload
         uses: actions/upload-artifact@v3
         with:
-          name: xml-libs
+          name: xmllibs-${{ matrix.host }}
           path: /usr/local
+          if-no-files-found: error

scripts/install_deps.sh

@@ -28,7 +28,7 @@ install_lib() {
     cd build-${HOST-native}
     ../configure $configure_args "$@"
     make --no-print-directory -j`nproc`
-    sudo make --no-print-directory install
+    ${SUDO-sudo} make --no-print-directory install
     cd ../..
 }