Add backwards compatibility tests using downloaded files #311

	name: lcg_linux_with_podio

	on: [push, pull_request]

	jobs:
	build-and-test-with-podio:
	runs-on: ubuntu-latest
	strategy:
	fail-fast: false
	matrix:
	LCG: ["dev3/x86_64-el9-clang16-opt",
	"dev4/x86_64-el9-clang16-opt",
	"dev4/x86_64-el9-gcc13-opt",
	"LCG_106/x86_64-el9-gcc13-opt"]
	CXX_STANDARD: [20]
	steps:
	- uses: actions/checkout@v4
	- uses: actions/checkout@v4
	with:
	repository: AIDASoft/podio
	path: podio
	- uses: cvmfs-contrib/github-action-cvmfs@v4
	- uses: aidasoft/run-lcg-view@v4
	with:
	release-platform: ${{ matrix.LCG }}
	run: \|
	STARTDIR=$(pwd)
	echo "::group::Build podio"
	cd podio
	echo "Building podio @"$(git log -1 --format=%H)
	cmake -DCMAKE_CXX_STANDARD=${{ matrix.CXX_STANDARD }} \
	-DENABLE_SIO=ON \
	-DENABLE_RNTUPLE=ON \
	-DENABLE_DATASOURCE=ON \
	-DBUILD_TESTING=OFF \
	-DCMAKE_INSTALL_PREFIX=$(pwd)/install \
	-G Ninja -B build
	cmake --build build --target install -- -k0
	source init.sh && source env.sh
	echo "::endgroup::"
	echo "::group::Build edm4hep"
	cd $STARTDIR
	echo "Building edm4hep"
	cmake -DCMAKE_CXX_STANDARD=${{ matrix.CXX_STANDARD }} \
	-DCMAKE_INSTALL_PREFIX=$(pwd)/install \
	-DUSE_EXTERNAL_CATCH2=OFF \
	-G Ninja -B build
	cmake --build build -- -k0
	ctest --test-dir build --output-on-failure
	cmake --build build --target install
	echo "::endgroup::"
	echo "::group::Test downstream usage"
	export CMAKE_PREFIX_PATH=$PWD/install:$CMAKE_PREFIX_PATH
	cd test/downstream-project-cmake-test
	cmake -DCMAKE_CXX_STANDARD=${{ matrix.CXX_STANDARD }} \
	-DCMAKE_INSTALL_PREFIX=$(pwd)/install \
	-G Ninja -B build
	cmake --build build -- -k0
	echo "::endgroup::"

Provide feedback