ci: add workaround for permission problems

As suggested here: actions/checkout#760

.github/workflows/ci.yaml

@@ -9,6 +9,7 @@ jobs:
  steps:
  - run: apk --no-cache add git gcc g++ binutils pkgconf meson ninja musl-dev wayland-dev wayland-protocols libinput-dev libevdev-dev libxkbcommon-dev pixman-dev glm-dev libdrm-dev mesa-dev cairo-dev pango-dev eudev-dev libxml2-dev libexecinfo-dev libseat-dev libxcb-dev xcb-util-wm-dev xwayland
  - uses: actions/checkout@v1
+ - run: git config --global --add safe.directory /__w/wayfire/wayfire
  - run: git submodule sync --recursive && git submodule update --init --force --recursive
  - run: meson build
  - run: ninja -v -Cbuild
@@ -24,6 +25,7 @@ jobs:
 
  # Build Wayfire
  - uses: actions/checkout@v1
+ - run: git config --global --add safe.directory /__w/wayfire/wayfire
  - run: git submodule sync --recursive && git submodule update --init --force --recursive
  - run: env CC=clang CXX=clang++ CXXFLAGS="-stdlib=libc++" LDFLAGS="-fuse-ld=lld -stdlib=libc++" meson build
  - run: ninja -v -Cbuild