Merge pull request #12842 from Neui/fix-cmake-ccache

CMake: Fix CCache support when already using _LAUNCHER

CMake/CCache.cmake

@@ -1,10 +1,17 @@
 find_program(CCACHE_BIN NAMES ccache sccache)
 if(CCACHE_BIN)
-    set_property(GLOBAL PROPERTY RULE_LAUNCH_COMPILE ${CCACHE_BIN})
+    # Official ccache recommendation is to set CMAKE_C(XX)_COMPILER_LAUNCHER
+    if (NOT CMAKE_C_COMPILER_LAUNCHER MATCHES "ccache")
+        list(INSERT CMAKE_C_COMPILER_LAUNCHER 0 "${CCACHE_BIN}")
+    endif()
+
+    if (NOT CMAKE_CXX_COMPILER_LAUNCHER MATCHES "ccache")
+        list(INSERT CMAKE_CXX_COMPILER_LAUNCHER 0 "${CCACHE_BIN}")
+    endif()
 
     # ccache uses -I when compiling without preprocessor, which makes clang complain.
     if("${CMAKE_CXX_COMPILER_ID}" STREQUAL "Clang")
-        set (CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Qunused-arguments -fcolor-diagnostics")
         set (CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -Qunused-arguments -fcolor-diagnostics")
+        set (CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Qunused-arguments -fcolor-diagnostics")
     endif()
 endif()