Meta+CI: Hook up the Lagom tools build with vcpkg

AK will depend on some vcpkg dependencies, so the Lagom tools build will
need to know how to use vcpkg. We can do this by sym-linking vcpkg.json
to Meta/Lagom (as vcpkg.json has to be in the CMake source directory).
We also need a CMakePresets.json in the source directory, which can just
include the root file. The root CMakePresets then needs to define paths
relative to ${fileDir} rather than ${sourceDir}.

.github/workflows/lagom-template.yml

@@ -104,21 +104,20 @@ jobs:
         run: |
           set -e
 
-          cmake -GNinja -S Meta/Lagom -B ${{ github.workspace }}/tools-build \
+          cmake --preset=CI -S Meta/Lagom -B ${{ github.workspace }}/Build/tools-build \
             -DLAGOM_TOOLS_ONLY=ON \
             -DINSTALL_LAGOM_TOOLS=ON \
-            -DCMAKE_INSTALL_PREFIX=${{ github.workspace }}/tool-install \
-            -DSERENITY_CACHE_DIR=${{ github.workspace }}/Build/caches \
+            -DCMAKE_INSTALL_PREFIX=${{ github.workspace }}/Build/tools-install \
             -DCMAKE_C_COMPILER=gcc-13 \
             -DCMAKE_CXX_COMPILER=g++-13 \
             -Dpackage=LagomTools
 
-          ninja -C tools-build install
+          ninja -C ${{ github.workspace }}/Build/tools-build install
 
           cmake --preset Fuzzers_CI -B Build \
             -DCMAKE_C_COMPILER=${{ steps.build-parameters.outputs.host_cc }} \
             -DCMAKE_CXX_COMPILER=${{ steps.build-parameters.outputs.host_cxx }} \
-            -DCMAKE_PREFIX_PATH=${{ github.workspace }}/tool-install
+            -DCMAKE_PREFIX_PATH=${{ github.workspace }}/Build/tools-install
 
       # === BUILD ===