qtwebengine not respecting CMAKE_INSTALL_PREFIX

"-DCMAKE_INSTALL_PREFIX=E:/qt6-update/packages/qtwebengine_x64-windows/debug"

-- Installing: E:/qt6-update/installed/x64-windows/share/Qt6BuildInternals/../../lib/Qt6WebEngineCored.lib

cmd /c "cd ../../x64-windows-dbg && "C:/Program Files/CMake/bin/cmake.exe" "E:/qt6-update/buildtrees/qtwebengine/src/2.0-alpha1-42e01529a7" "-DQT_NO_MAKE_EXAMPLES:BOOL=TRUE" "-DQT_NO_MAKE_TESTS:BOOL=TRUE" "-DHOST_PERL:PATH="E:/vcpkg_cache/downloads/tools/perl/5.30.0.1/perl/bin/perl.exe"" "-DINSTALL_BINDIR:STRING=bin" "-DINSTALL_LIBEXECDIR:STRING=bin" "-DINSTALL_PLUGINSDIR:STRING=Qt6/plugins" "-DINSTALL_QMLDIR:STRING=Qt6/qml" "-DGPerf_EXECUTABLE=E:/vcpkg_cache/downloads/tools/gperf/bin/gperf.exe" "-DBISON_EXECUTABLE=E:/vcpkg_cache/downloads/tools/winflexbison/0a14154bff-a8cf65db07/win_bison.exe" "-DFLEX_EXECUTABLE=E:/vcpkg_cache/downloads/tools/winflexbison/0a14154bff-a8cf65db07/win_flex.exe" "-DPython2_EXECUTABLE=E:/vcpkg_cache/downloads/tools/python/python-2.7.18-x64/python.exe" "-DNodejs_EXECUTABLE=E:/vcpkg_cache/downloads/tools/nodejs/node-v16.4.1-win-x86/node.exe" "-DQT_SYNCQT:PATH="E:/qt6-update/installed/x64-windows/tools/Qt6/bin/syncqt.pl"" "-DCMAKE_MAKE_PROGRAM=E:/vcpkg_cache/downloads/tools/ninja/1.10.2-windows/ninja.exe" "-DBUILD_SHARED_LIBS=ON" "-DVCPKG_CHAINLOAD_TOOLCHAIN_FILE=E:/qt6-update/scripts/toolchains/windows.cmake" "-DVCPKG_TARGET_TRIPLET=x64-windows" "-DVCPKG_SET_CHARSET_FLAG=ON" "-DVCPKG_PLATFORM_TOOLSET=v142" "-DCMAKE_EXPORT_NO_PACKAGE_REGISTRY=ON" "-DCMAKE_FIND_PACKAGE_NO_PACKAGE_REGISTRY=ON" "-DCMAKE_FIND_PACKAGE_NO_SYSTEM_PACKAGE_REGISTRY=ON" "-DCMAKE_INSTALL_SYSTEM_RUNTIME_LIBS_SKIP=TRUE" "-DCMAKE_VERBOSE_MAKEFILE=ON" "-DVCPKG_APPLOCAL_DEPS=OFF" "-DCMAKE_TOOLCHAIN_FILE=E:/qt6-update/scripts/buildsystems/vcpkg.cmake" "-DCMAKE_ERROR_ON_ABSOLUTE_INSTALL_DESTINATION=ON" "-DVCPKG_CXX_FLAGS=" "-DVCPKG_CXX_FLAGS_RELEASE=" "-DVCPKG_CXX_FLAGS_DEBUG=" "-DVCPKG_C_FLAGS=" "-DVCPKG_C_FLAGS_RELEASE=" "-DVCPKG_C_FLAGS_DEBUG=" "-DVCPKG_CRT_LINKAGE=dynamic" "-DVCPKG_LINKER_FLAGS=" "-DVCPKG_LINKER_FLAGS_RELEASE=" "-DVCPKG_LINKER_FLAGS_DEBUG=" "-DVCPKG_TARGET_ARCHITECTURE=x64" "-DCMAKE_INSTALL_LIBDIR:STRING=lib" "-DCMAKE_INSTALL_BINDIR:STRING=bin" "-D_VCPKG_ROOT_DIR=E:/qt6-update" "-D_VCPKG_INSTALLED_DIR=E:/qt6-update/installed" "-DVCPKG_MANIFEST_INSTALL=OFF" "-DINPUT_debug:BOOL=ON" "-DINSTALL_DOCDIR:STRING=../doc/Qt6/" "-DINSTALL_INCLUDEDIR:STRING=../include/Qt6/" "-DINSTALL_TRANSLATIONSDIR:STRING=../translations/Qt6/" "-DINSTALL_DESCRIPTIONSDIR:STRING=../share/Qt6/modules" "-DINSTALL_MKSPECSDIR:STRING=../share/Qt6/mkspecs" "-G" "Ninja" "-DCMAKE_BUILD_TYPE=Debug" "-DCMAKE_INSTALL_PREFIX=E:/qt6-update/packages/qtwebengine_x64-windows/debug""