Add ccache option (colmap#1395)

CMakeLists.txt

@@ -63,6 +63,7 @@ option(OPENGL_ENABLED "Whether to enable OpenGL, if available" ON)
 option(TESTS_ENABLED "Whether to build test binaries" OFF)
 option(ASAN_ENABLED "Whether to enable AddressSanitizer flags" OFF)
 option(PROFILING_ENABLED "Whether to enable google-perftools linker flags" OFF)
+option(CCACHE_ENABLED "Whether to enable compiler caching, if available" ON)
 option(CGAL_ENABLED "Whether to enable the CGAL library" ON)
 option(BOOST_STATIC "Whether to enable static boost library linker flags" ON)
 set(CUDA_ARCHS "Auto" CACHE STRING "List of CUDA architectures for which to \
@@ -254,6 +255,19 @@ else()
     message(STATUS "Disabling OpenGL support")
 endif()
 
+if(CCACHE_ENABLED)
+    find_program(CCACHE ccache)
+    if(CCACHE)
+        message(STATUS "Enabling ccache support")
+        set(CMAKE_C_COMPILER_LAUNCHER ${CCACHE})
+        set(CMAKE_CXX_COMPILER_LAUNCHER ${CCACHE})
+    else()
+        message(STATUS "Disabling ccache support")
+    endif()
+else()
+    message(STATUS "Disabling ccache support")
+endif()
+
 if(PROFILING_ENABLED)
     message(STATUS "Enabling profiling support")
     set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -lprofiler -ltcmalloc")