GHA: adjust CMake invocation for libxml2 usage

Use the CMake CONFIG definitions to wire up LibXml2 rather than trying
to manually add the dependencies.

Author: compnerd

.github/workflows/swift-toolchain.yml

@@ -970,6 +970,7 @@ jobs:
                 -D CMAKE_Swift_COMPILER_WORKS=YES `
                 -D CMAKE_Swift_FLAGS="-sdk `"${SDKROOT}`" -Xcc -D_ALLOW_COMPILER_AND_STL_VERSION_MISMATCH" `
                 -D CMAKE_EXE_LINKER_FLAGS="${{ inputs.WINDOWS_CMAKE_EXE_LINKER_FLAGS }}" `
+                -D CMAKE_FIND_PACKAGE_PREFER_CONFIG=YES `
                 -D CMAKE_INSTALL_PREFIX=${{ github.workspace }}/BuildRoot/Library/Developer/Toolchains/unknown-Asserts-development.xctoolchain/usr `
                 -D CMAKE_SHARED_LINKER_FLAGS="${{ inputs.WINDOWS_CMAKE_SHARED_LINKER_FLAGS }}" `
                 ${CMAKE_SYSTEM_NAME} `
@@ -1004,8 +1005,7 @@ jobs:
                 -D CLANG_VENDOR=compnerd.org `
                 -D CLANG_VENDOR_UTI=org.compnerd.dt `
                 -D cmark-gfm_DIR=${{ github.workspace }}/BinaryCache/Library/cmark-gfm-${{ inputs.swift_cmark_version }}/usr/lib/cmake `
-                -D LIBXML2_INCLUDE_DIR=${{ github.workspace }}/BinaryCache/Library/libxml2-${{ inputs.libxml2_version }}/usr/include/libxml2 `
-                -D LIBXML2_LIBRARY=${{ github.workspace }}/BinaryCache/Library/libxml2-${{ inputs.libxml2_version }}/usr/lib/libxml2s.lib `
+                -D LibXml2_DIR=${{ github.workspace }}/BinaryCache/Library/libxml2-${{ inputs.libxml2_version }}/usr/lib/Windows/${{ matrix.cpu }}/cmake/libxml2-${{ inputs.libxml2_version }} `
                 -D PACKAGE_VENDOR=compnerd.org `
                 -D SWIFT_VENDOR=compnerd.org `
                 -D LLVM_PARALLEL_LINK_JOBS=2 `
@@ -2155,6 +2155,7 @@ jobs:
                 -D CMAKE_CXX_COMPILER_TARGET=${{ matrix.triple }} `
                 -D CMAKE_CXX_FLAGS="${{ matrix.cxxflags }}" `
                 -D CMAKE_EXE_LINKER_FLAGS="${{ inputs.WINDOWS_CMAKE_EXE_LINKER_FLAGS }}" `
+                -D CMAKE_FIND_PACKAGE_PREFER_CONFIG=YES `
                 -D CMAKE_MT=mt `
                 -D CMAKE_INSTALL_PREFIX=${{ github.workspace }}/BuildRoot/Library/Developer/Platforms/${{ matrix.os }}.platform/Developer/SDKs/${{ matrix.os }}.sdk/usr `
                 -D CMAKE_Swift_COMPILER=${SWIFTC} `
@@ -2179,9 +2180,7 @@ jobs:
                 -D _SwiftFoundation_SourceDIR=$SWIFT_FOUNDATION_SOURCE_DIR `
                 -D _SwiftFoundationICU_SourceDIR=$SWIFT_FOUNDATION_ICU_SOURCE_DIR `
                 -D _SwiftCollections_SourceDIR=$SWIFT_COLLECTIONS_SOURCE_DIR `
-                -D LIBXML2_DEFINITIONS="${DEFINITION_FLAG}LIBXML_STATIC" `
-                -D LIBXML2_INCLUDE_DIR=${{ github.workspace }}/BuildRoot/Library/libxml2-${{ inputs.libxml2_version }}/usr/include/libxml2 `
-                -D LIBXML2_LIBRARY=${{ github.workspace }}/BuildRoot/Library/libxml2-${{ inputs.libxml2_version }}/usr/lib/$LIBXML `
+                -D LibXml2_DIR=${{ github.workspace }}/BuildRoot/Library/libxml2-${{ inputs.libxml2_version }}/usr/lib/Windows/${{ matrix.cpu }}/cmake/libxml2-${{ inputs.libxml2_version }} `
                 -D ZLIB_ROOT=${{ github.workspace }}/BuildRoot/Library/zlib-${{ inputs.zlib_version }}/usr `
                 -D ZLIB_LIBRARY=${{ github.workspace }}/BuildRoot/Library/zlib-${{ inputs.zlib_version }}/usr/lib/$LIBZ `
                 -D SwiftFoundation_MACRO=${{ github.workspace }}/BinaryCache/Library/Developer/Toolchains/unknown-Asserts-development.xctoolchain/usr/bin