meson: add tests (#1044)

This integrates the "main" test suite (test/test.cc) in Meson.

This allows to run the tests in the CI with the Meson-built version of
the library to ensure that nothing breaks unexpectedly.

It also simplifies life of downstream packagers, that do not have to
write a custom build script to split the library and run tests but can
instead just let Meson do that for them.

.github/workflows/test.yaml

@@ -39,3 +39,55 @@ jobs:
         cd test
         msbuild.exe test.sln /verbosity:minimal /t:Build "/p:Configuration=Release;Platform=x64"
         x64\Release\test.exe
+
+
+  meson-build:
+    runs-on: ${{ matrix.os }}
+
+    strategy:
+      matrix:
+        os: [macos-latest, ubuntu-latest, windows-latest]
+
+    steps:
+    - name: Prepare Git for checkout on Windows
+      if: matrix.os == 'windows-latest'
+      run: |
+        git config --global core.autocrlf false
+        git config --global core.eol lf
+
+    - uses: actions/checkout@v2
+
+    - name: Install dependencies on Linux
+      if: matrix.os == 'ubuntu-latest'
+      run: sudo apt-get -qq update && sudo apt-get -qq install meson libssl-dev zlib1g-dev libbrotli-dev libgtest-dev
+
+    - name: Install dependencies on MacOS
+      if: matrix.os == 'macos-latest'
+      run: brew install meson openssl brotli googletest
+
+    - name: Setup MSVC on Windows
+      if: matrix.os == 'windows-latest'
+      uses: ilammy/msvc-dev-cmd@v1
+
+    # It is necessary to remove MinGW and StrawberryPerl as they both provide
+    # GCC. This causes issues because CMake prefers to use MSVC, while Meson
+    # uses GCC, if found, causing linking errors.
+    - name: Install dependencies on Windows
+      if: matrix.os == 'windows-latest'
+      run: |
+        choco uninstall mingw strawberryperl --yes --all-versions --remove-dependencies --skip-autouninstaller --no-color
+        Remove-Item -Path C:\Strawberry -Recurse
+        choco install pkgconfiglite --yes --skip-virus-check --no-color
+        pip install meson ninja
+        Invoke-WebRequest -Uri https://github.com/google/googletest/archive/refs/heads/master.zip -OutFile googletest-master.zip
+        Expand-Archive -Path googletest-master.zip
+        cd googletest-master\googletest-master
+        cmake -S . -B build -DINSTALL_GTEST=ON -DBUILD_GMOCK=OFF -Dgtest_hide_internal_symbols=ON -DCMAKE_INSTALL_PREFIX=C:/googletest
+        cmake --build build --config=Release
+        cmake --install build --config=Release
+        cd ..\..
+
+    - name: Build and test
+      run: |
+        meson setup build -Dcpp-httplib_test=true -Dpkg_config_path=C:\googletest\lib\pkgconfig -Db_vscrt=static_from_buildtype
+        meson test --no-stdsplit --print-errorlogs -C build