depends(libxkbcommon): explicit xkb extension paths for cross + cache restore-keys

libxkbcommon 1.13.1 meson.build adds empty pkgconfig vars when xkeyboard-config is absent from the cross sysroot (XKEYBOARD_CONFIG_ROOT='') while has_extensions_directories is true -> meson hard-errors at pkgconfig.generate. Pass non-empty -Dxkb-config-(un)versioned-extensions-path.

Add restore-keys to all 4 depends cache restores: a busted exact key (any packages/* edit) now falls back to the newest prefix match, so make resumes from the partial built tree instead of rebuilding the static-Qt6 toolchain from scratch.

.github/workflows/build.yml

@@ -166,12 +166,16 @@ jobs:
         with:
           path: contrib/depends/sources
           key: depends-sources-${{ hashFiles('contrib/depends/packages/*') }}
+          restore-keys: |
+            depends-sources-
       - name: restore depends built cache (mingw)
         id: cache-built
         uses: actions/cache/restore@v4
         with:
           path: contrib/depends/built
           key: depends-built-mingw32-${{ hashFiles('contrib/depends/packages/*', 'contrib/depends/hosts/*', 'contrib/depends/toolchain.cmake.in') }}
+          restore-keys: |
+            depends-built-mingw32-
       - name: build depends (static Qt6 + tor + boost + openssl for mingw)
         # -j2 not -j(nproc): the parallel static Qt6 compile OOMs the 16G runner at -j4. Slower but safe.
         run: make -C contrib/depends HOST="$HOST" -j2
@@ -276,12 +280,16 @@ jobs:
         with:
           path: contrib/depends/sources
           key: depends-sources-${{ hashFiles('contrib/depends/packages/*') }}
+          restore-keys: |
+            depends-sources-
       - name: restore depends built cache
         id: cache-built
         uses: actions/cache/restore@v4
         with:
           path: contrib/depends/built
           key: depends-built-${{ matrix.host }}-${{ hashFiles('contrib/depends/packages/*', 'contrib/depends/hosts/*', 'contrib/depends/toolchain.cmake.in') }}
+          restore-keys: |
+            depends-built-${{ matrix.host }}-
       - name: build depends (static Qt6 + tor + boost + openssl)
         run: make -C contrib/depends HOST="$HOST" -j2
       - name: save depends sources cache