Use GitHub Actions as CI service (#5602)

* ci: migrate to GitHub Actions

* ci: linux-mingw: use lief for parsing PE files

* ci: fix left-over issues with clang-format check

* ci: workaround libc++ issue on macOS

* appveyor: remove build scripts

* README: add GitHub Actions badge and ...

remove Travis CI and Appveyor badges

.ci/linux-frozen/docker.sh

@@ -0,0 +1,15 @@
+#!/bin/bash -ex
+
+mkdir -p ~/bin/gold
+echo '#!/bin/bash' > ~/bin/gold/ld
+echo 'gold "$@"' >> ~/bin/gold/ld
+chmod a+x ~/bin/gold/ld
+export CFLAGS="-B$HOME/bin/gold $CFLAGS"
+export CXXFLAGS="-B$HOME/bin/gold $CXXFLAGS"
+
+
+mkdir build && cd build
+cmake .. -G Ninja -DCMAKE_BUILD_TYPE=Debug -DCMAKE_C_COMPILER=/usr/lib/ccache/gcc -DCMAKE_CXX_COMPILER=/usr/lib/ccache/g++
+ninja
+
+ctest -VV -C Release