message: Add a dedicated CMake option for building gltfpack.
  On systems that have GLFW installed the MESHOPT_BUILD_TOOLS option would
  otherwise build the internal lodviewer tool as well, which might not be
  desirable.
diff: @@ -12,6 +12,7 @@ endif()
  project(meshoptimizer VERSION 0.14 LANGUAGES CXX)
  option(MESHOPT_BUILD_DEMO "Build demo" OFF)
  +option(MESHOPT_BUILD_GLTFPACK "Build gltfpack" OFF)
  option(MESHOPT_BUILD_TOOLS "Build tools" OFF)
  option(MESHOPT_BUILD_SHARED_LIBS "Build shared libraries" OFF)
  set(MESHOPT_BUILD_TOOLS_GLFW_FOLDER_NAME "" CACHE STRING "Custom folder to look for GLFW")
  @@ -84,7 +85,7 @@ if(MESHOPT_BUILD_DEMO)
  target_link_libraries(demo meshoptimizer)
  endif()
  -if(MESHOPT_BUILD_TOOLS)
  +if(MESHOPT_BUILD_GLTFPACK)
  add_executable(gltfpack ${GLTF_SOURCES} tools/meshloader.cpp)
  target_link_libraries(gltfpack meshoptimizer)
  list(APPEND TARGETS gltfpack)
  @@ -93,7 +94,9 @@ if(MESHOPT_BUILD_TOOLS)
  string(CONCAT RPATH "$ORIGIN/../" ${CMAKE_INSTALL_LIBDIR})
  set_target_properties(gltfpack PROPERTIES INSTALL_RPATH ${RPATH})
  endif()
  +endif()
  +if(MESHOPT_BUILD_TOOLS)
  if(NOT (MESHOPT_BUILD_TOOLS_GLFW_FOLDER_NAME STREQUAL ""))
  message(STATUS "Using GLFW3 from: ${MESHOPT_BUILD_TOOLS_GLFW_FOLDER_NAME}")
  set(GLFW_BUILD_EXAMPLES OFF CACHE BOOL "")
  