This commit continas:

1. Enable cache if available:
2. The function to prevent in-source builds

CMakeLists.txt

@@ -99,6 +99,12 @@ if(INSTANCES_ONLY)
     set(CK_ENABLE_INSTANCES_ONLY "ON")
 endif()
 
+# enable prevent in source build
+include(PreventInSourceBuilds)
+
+# enable cache system
+include(Cache)
+
 include(getopt)
 
 # CK version file to record release version as well as git commit hash

cmake/Cache.cmake

+option(ENABLE_CACHE "Enable cache if available" ON)
+if(NOT ENABLE_CACHE)
+  return()
+endif()
+
+set(CACHE_OPTION
+    "sccache"
+    CACHE STRING "Compiler cache to be used")
+set(CACHE_OPTION_VALUES "sccache" "ccache")
+set_property(CACHE CACHE_OPTION PROPERTY STRINGS ${CACHE_OPTION_VALUES})
+list(
+  FIND
+  CACHE_OPTION_VALUES
+  ${CACHE_OPTION}
+  CACHE_OPTION_INDEX)
+
+if(${CACHE_OPTION_INDEX} EQUAL -1)
+  message(
+    STATUS
+      "Using custom compiler cache system: '${CACHE_OPTION}', explicitly supported entries are ${CACHE_OPTION_VALUES}")
+endif()
+
+find_program(CACHE_BINARY ${CACHE_OPTION})
+if(CACHE_BINARY)
+  message(STATUS "${CACHE_OPTION} found and enabled")
+  set(CMAKE_CXX_COMPILER_LAUNCHER ${CACHE_BINARY})
+  set(CMAKE_C_COMPILER_LAUNCHER ${CACHE_BINARY})
+else()
+  message(WARNING "${CACHE_OPTION} is enabled but was not found. Not using it")
+endif()

cmake/PreventInSourceBuilds.cmake

+function(AssureOutOfSourceBuilds)
+  get_filename_component(srcdir "${CMAKE_SOURCE_DIR}" REALPATH)
+  get_filename_component(bindir "${CMAKE_BINARY_DIR}" REALPATH)
+
+  if("${srcdir}" STREQUAL "${bindir}")
+    message("Warning: in-source builds are disabled")
+    message("Please create a separate build directory and run cmake from there")
+    message(FATAL_ERROR "Quitting configuration")
+  endif()
+endfunction()
+
+assureOutOfSourceBuilds()