New in version 3.17.

This is a CMake Environment Variable. Its initial value is taken from the calling process environment.

Default compiler launcher to use for the specified language. Will only be used by CMake to initialize the variable on the first configuration. Afterwards, it is available through the cache setting of the variable of the same name. For any configuration run (including the first), the environment variable will be ignored if the CMAKE_<LANG>_COMPILER_LAUNCHER variable is defined.