CI: install correct version of libomp

actions/runner-images@15a6106
changed the default version of Clang from 10 to 11, but `apt-get install
libomp-dev` still installs libomp-10-dev. Ideally, the correct version
of libomp would already be pre-installed (see
actions/runner-images#3506), but for now make sure we install the
correct version.

Signed-off-by: Omar Sandoval <osandov@osandov.com>

.github/workflows/ci.yml

@@ -22,7 +22,7 @@ jobs:
       - name: Install dependencies
         run: |
           sudo apt-get update
-          sudo apt-get install busybox-static libelf-dev libdw-dev qemu-kvm zstd ${{ matrix.cc == 'clang' && 'libomp-dev' || '' }}
+          sudo apt-get install busybox-static libelf-dev libdw-dev qemu-kvm zstd ${{ matrix.cc == 'clang' && 'libomp-$(clang --version | sed -rn "s/.*clang version ([0-9]+).*/\\1/p")-dev' || '' }}
           pip install mypy
       - name: Generate version.py
         run: python setup.py --version