fix for ubuntu being horribly outdated once more

>:(
(This took me so long to notice, but this fucking runner defaults to a non standard version of pkg-config,which, at the point that this outdated pos version of ubuntu provides, does NOT seem to support the define-prefix flag or something)

Author: HeliumAnt

.github/workflows/meson.yml

@@ -175,6 +175,8 @@ jobs:
         env:
           OSXCROSS_MACPORTS_MIRROR: "https://packages.macports.org"
         run: |
+          echo "::group::Installing pkg-config"
+          sudo apt install pkg-config
           echo "::group::Installing mac deps"
           omp install libsdl2 onetbb lz4 libpng minizip luajit flac
           echo "OSXCROSS_PKG_CONFIG_PATH=${{env.OSXCROSS_TARGET}}/macports/pkgs/opt/local/libexec/onetbb/lib/pkgconfig" >> $GITHUB_ENV