add text for ccache in makefile to prevent confusing Ninja user (#2346)

* add necessary text for ccache in makefile to prevent confusing Ninja user

* typo fix

* textual

CMakeLists.txt

@@ -88,12 +88,12 @@ if(USE_CCACHE)
 	if(CCACHE_FOUND)
 		set(CMAKE_CXX_COMPILER_LAUNCHER ${CCACHE_FOUND})
 		set(CMAKE_C_COMPILER_LAUNCHER ${CCACHE_FOUND})
-		message(STATUS "Using ccache, please keep an eye on this because sometimes it's not quite stable and generated unusable binary.\n-- use `cmake -DUSE_CCACHE=OFF ..` to turn off ccache")
+		message(STATUS "Using ccache, please keep an eye on this because sometimes it's not quite stable and generated unusable binary.\n-- use `cmake -DUSE_CCACHE=OFF ..` (pure cmake) or `cmake -G Ninja -DUSE_CCACHE=OFF .. ` (cmake with Ninja) to turn off ccache")
 	else()
 		message(WARNING "ccache is enabled but not found on the system.")
 	endif()
 else()
-	message(STATUS "Not using ccache, use `cmake -DUSE_CCACHE=ON ..` to turn on ccache")
+	message(STATUS "Not using ccache, use `cmake -DUSE_CCACHE=ON ..` (pure cmake) or `cmake -G Ninja -DUSE_CCACHE=ON ..` (cmake with Ninja) to turn on ccache")
 endif()
 message(STATUS "-------^ ccache info--------")