Android: Integrate vcpkg with Gradle build

This ensures that vcpkg downloads and builds all dependencies for
Android. We add it as a CMAKE_TOOLCHAIN_FILE that then chainloads the
Android NDK's toolchain file, as per the vcpkg documentation.

Ladybird/Android/BuildLagomTools.sh

@@ -4,24 +4,39 @@ set -eo pipefail
 
 DIR="$( cd "$( dirname "${BASH_SOURCE[0]}" )" && pwd )"
 
-SERENITY_ROOT="$(realpath "${DIR}"/../..)"
+LADYBIRD_SOURCE_DIR="$(realpath "${DIR}"/../..)"
 
 # shellcheck source=/dev/null
-. "${SERENITY_ROOT}/Meta/shell_include.sh"
+. "${LADYBIRD_SOURCE_DIR}/Meta/shell_include.sh"
 
 # shellcheck source=/dev/null
-. "${SERENITY_ROOT}/Meta/find_compiler.sh"
+. "${LADYBIRD_SOURCE_DIR}/Meta/find_compiler.sh"
 
 pick_host_compiler
 
-BUILD_DIR=${BUILD_DIR:-"${SERENITY_ROOT}/Build"}
+BUILD_DIR=${BUILD_DIR:-"${LADYBIRD_SOURCE_DIR}/Build"}
 CACHE_DIR=${CACHE_DIR:-"${BUILD_DIR}/caches"}
 
-cmake -S "$SERENITY_ROOT/Meta/Lagom" -B "$BUILD_DIR/lagom-tools" \
+# HACK: This export of XDG_CACHE_HOME is required to make vcpkg happy.
+# This is because vcpkg tries to find a cache directory by:
+#   1) checking $XDG_CACHE_HOME
+#   2) appending "/.cache" to $HOME
+# The problem is, in the Android build environment, neither of those environment variables are set.
+# This causes vcpkg to fail; so, we set a dummy $XDG_CACHE_HOME, ensuring that vcpkg is happy.
+# (Note that vcpkg appends "/vcpkg" to the cache directory we give it.)
+# (And this also works on macOS, despite the fact that $XDG_CACHE_HOME is a Linux-ism.)
+export XDG_CACHE_HOME="$CACHE_DIR"
+
+cmake -S "${LADYBIRD_SOURCE_DIR}/Meta/Lagom" -B "$BUILD_DIR/lagom-tools" \
     -GNinja -Dpackage=LagomTools \
     -DCMAKE_INSTALL_PREFIX="$BUILD_DIR/lagom-tools-install"  \
     -DCMAKE_C_COMPILER="$CC" \
     -DCMAKE_CXX_COMPILER="$CXX" \
-    -DSERENITY_CACHE_DIR="$CACHE_DIR"
+    -DSERENITY_CACHE_DIR="$CACHE_DIR" \
+    -DCMAKE_TOOLCHAIN_FILE="$LADYBIRD_SOURCE_DIR/Toolchain/Tarballs/vcpkg/scripts/buildsystems/vcpkg.cmake" \
+    -DVCPKG_INSTALL_OPTIONS="--no-print-usage" \
+    -DVCPKG_OVERLAY_TRIPLETS="$LADYBIRD_SOURCE_DIR/Meta/CMake/vcpkg/release-triplets" \
+    -DVCPKG_ROOT="$LADYBIRD_SOURCE_DIR/Toolchain/Tarballs/vcpkg" \
+    -DVCPKG_MANIFEST_DIR="$LADYBIRD_SOURCE_DIR"
 
 ninja -C "$BUILD_DIR/lagom-tools" install