Adjust CMakeLists.txt files to use ccache when it's available.

CMakeLists.txt

@@ -25,6 +25,12 @@ if(RAPIDJSON_HAS_STDSTRING)
     add_definitions(-DRAPIDJSON_HAS_STDSTRING)
 endif()
 
+find_program(CCACHE_FOUND ccache)
+if(CCACHE_FOUND)
+    set_property(GLOBAL PROPERTY RULE_LAUNCH_COMPILE ccache)
+    set_property(GLOBAL PROPERTY RULE_LAUNCH_LINK ccache)
+endif(CCACHE_FOUND)
+
 if ("${CMAKE_CXX_COMPILER_ID}" STREQUAL "GNU")
     set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -march=native -Wall -Wextra -Werror")
 elseif (CMAKE_CXX_COMPILER_ID MATCHES "Clang")

test/perftest/CMakeLists.txt

@@ -9,6 +9,12 @@ target_link_libraries(perftest ${TEST_LIBRARIES})
 
 add_dependencies(tests perftest)
 
+find_program(CCACHE_FOUND ccache)
+if(CCACHE_FOUND)
+    set_property(GLOBAL PROPERTY RULE_LAUNCH_COMPILE ccache)
+    set_property(GLOBAL PROPERTY RULE_LAUNCH_LINK ccache)
+endif(CCACHE_FOUND)
+
 IF(NOT (CMAKE_BUILD_TYPE STREQUAL "Debug"))
 add_test(NAME perftest
     COMMAND ${CMAKE_RUNTIME_OUTPUT_DIRECTORY}/perftest

test/unittest/CMakeLists.txt

@@ -18,6 +18,12 @@ set(UNITTEST_SOURCES
     valuetest.cpp
     writertest.cpp)
 
+find_program(CCACHE_FOUND ccache)
+if(CCACHE_FOUND)
+    set_property(GLOBAL PROPERTY RULE_LAUNCH_COMPILE ccache)
+    set_property(GLOBAL PROPERTY RULE_LAUNCH_LINK ccache)
+endif(CCACHE_FOUND)
+
 if ("${CMAKE_CXX_COMPILER_ID}" STREQUAL "GNU")
     set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Werror -Wall -Wextra -Weffc++ -Wswitch-default -Wfloat-equal")
 elseif (CMAKE_CXX_COMPILER_ID MATCHES "Clang")