github/workflows: switch Ubuntu mingw-w64 build to pkgconf

Ubuntu 24.04's pkg-config is already an almost empty transitional
package that depends on pkgconf, and pkgconf contains the
`/usr/bin/pkg-config` binary.

Thus while we are moving macOS to it, we shall do the same with
this mingw-w64 build.

.github/workflows/build.yml

@@ -62,7 +62,7 @@ jobs:
         run: |
           sudo dpkg --add-architecture i386
           sudo apt-get update
-          sudo apt-get install -y ccache g++-mingw-w64 gcc-multilib meson nasm ninja-build pkg-config ${{ matrix.wine }}
+          sudo apt-get install -y ccache g++-mingw-w64 gcc-multilib meson nasm ninja-build pkgconf ${{ matrix.wine }}
 
       - name: Install Meson Wraps
         run: |