Fix Path for ROOT Includes

Under the Filesystem Hierarchy Standard, the includes should go to
<prefix>/include, not <prefix>/share/include...

cmake/build-root-submodule.cmake

@@ -99,7 +99,7 @@ include(GNUInstallDirs)
 install(DIRECTORY "${PROJECT_BINARY_DIR}/root_install/bin/" TYPE BIN USE_SOURCE_PERMISSIONS)
 install(DIRECTORY "${PROJECT_BINARY_DIR}/root_install/lib/" TYPE LIB USE_SOURCE_PERMISSIONS)
 install(DIRECTORY "${PROJECT_BINARY_DIR}/root_install/etc/" TYPE SYSCONF USE_SOURCE_PERMISSIONS)
-install(DIRECTORY "${PROJECT_BINARY_DIR}/root_install/include/" DESTINATION "${CMAKE_INSTALL_DATAROOTDIR}/include/root")
+install(DIRECTORY "${PROJECT_BINARY_DIR}/root_install/include/" DESTINATION "${CMAKE_INSTALL_PREFIX}/include/root")
 install(DIRECTORY "${PROJECT_BINARY_DIR}/root_install/fonts/" DESTINATION "${CMAKE_INSTALL_DATAROOTDIR}/fonts/truetype/")
 install(DIRECTORY "${PROJECT_BINARY_DIR}/root_install/man/" DESTINATION "${CMAKE_INSTALL_DATAROOTDIR}/man/")
 install(FILES "${PROJECT_BINARY_DIR}/root_install/LICENSE" DESTINATION "${CMAKE_INSTALL_DATAROOTDIR}/root/")