add gh workflow for checking of working installed version

microfix

add gh workflow part for pkgconfig

uncomment that should not be commented

move some add_subdirectory to logically correct place

.github/workflows/ubuntu_test_installed_version.yml

@@ -0,0 +1,59 @@
+name: ubuntu_test_installed_version.yml
+
+
+on:
+  push:
+    branches:
+      - master
+      - main
+  pull_request:
+    branches:
+      - master
+      - main
+
+env:
+  CTEST_OUTPUT_ON_FAILURE: 1
+  CPM_SOURCE_CACHE: ${{ github.workspace }}/cpm_modules
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+
+    steps:
+      - uses: actions/checkout@v3
+
+      - uses: actions/cache@v3
+        with:
+          path: "**/cpm_modules"
+          key: ${{ github.workflow }}-cpm-modules-${{ hashFiles('**/CMakeLists.txt', '**/*.cmake') }}
+
+      - name: install library
+        run: |
+          cmake -S. -Bbuild -DCMAKE_BUILD_TYPE=Release --log-level=DEBUG -DCMAKE_INSTALL_PREFIX=./install_dir
+          cmake --install ./build --prefix ./install_dir
+          rm -rf build
+
+      - name: configure with installed version via cmake
+        run: CMAKE_PREFIX_PATH="./install_dir" cmake -S. -Bbuild2 -DMAGIC_ENUM_OPT_TEST_INSTALLED_VERSION=1 --log-level=DEBUG
+
+      - name: build with installed version via cmake
+        run: cmake --build build2 --config Debug -j4 --verbose
+
+      - name: test
+        run: |
+          cd build2
+          ctest --build-config Debug -j4
+
+      - name: clear 
+        run: rm -rf build2
+
+      - name: configure with installed version via pkgconfig
+        run: CMAKE_PREFIX_PATH="./install_dir" cmake -S. -Bbuild3 -DMAGIC_ENUM_OPT_TEST_INSTALLED_VERSION_PKGCONFIG=1 -DPKG_CONFIG_USE_CMAKE_PREFIX_PATH=1 --log-level=DEBUG
+
+      - name: build with installed version via pkgconfig
+        run: cmake --build build3 --config Debug -j4 --verbose
+
+      - name: test
+        run: |
+          cd build3
+          ctest --build-config Debug -j4