CFLAGS

Default compilation flags to be used when compiling C files. Will only be used by CMake on the first configuration to determine CC default compilation flags, after which the value for CFLAGS is stored in the cache as CMAKE_C_FLAGS. For any configuration run (including the first), the environment variable will be ignored if the CMAKE_C_FLAGS variable is defined.

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Licensed under the BSD 3-clause License.
https://cmake.org/cmake/help/v3.11/envvar/CFLAGS.html