CMake: Allow specifying arbitrary CCACHE parameters

Introduces the LLVM_CCACHE_PARAMS cmake variable, which can be used to
pass arbitrary parameters to ccache invocations.

llvm-svn: 324779

Author: bogner

llvm/CMakeLists.txt

@@ -144,7 +144,10 @@ if(LLVM_CCACHE_BUILD)
   if(CCACHE_PROGRAM)
       set(LLVM_CCACHE_MAXSIZE "" CACHE STRING "Size of ccache")
       set(LLVM_CCACHE_DIR "" CACHE STRING "Directory to keep ccached data")
-      set(CCACHE_PROGRAM "CCACHE_CPP2=yes CCACHE_HASHDIR=yes ${CCACHE_PROGRAM}")
+      set(LLVM_CCACHE_PARAMS "CCACHE_CPP2=yes CCACHE_HASHDIR=yes"
+          CACHE STRING "Parameters to pass through to ccache")
+
+      set(CCACHE_PROGRAM "${LLVM_CCACHE_PARAMS} ${CCACHE_PROGRAM}")
       if (LLVM_CCACHE_MAXSIZE)
         set(CCACHE_PROGRAM "CCACHE_MAXSIZE=${LLVM_CCACHE_MAXSIZE} ${CCACHE_PROGRAM}")
       endif()
@@ -1022,4 +1025,3 @@ endif()
 if (MSVC AND CMAKE_HOST_SYSTEM_NAME STREQUAL "Windows")
   include(InstallRequiredSystemLibraries)
 endif()
-