CMAKE_NINJA_OUTPUT_PATH_PREFIX

Set output files path prefix for the Ninja generator.

Every output files listed in the generated build.ninja will be prefixed by the contents of this variable (a trailing slash is appended if missing). This is useful when the generated ninja file is meant to be embedded as a subninja file into a super ninja project. For example, a ninja build file generated with a command like:

cd top-build-dir/sub &&
cmake -G Ninja -DCMAKE_NINJA_OUTPUT_PATH_PREFIX=sub/ path/to/source

can be embedded in top-build-dir/build.ninja with a directive like this:

subninja sub/build.ninja

The auto-regeneration rule in top-build-dir/build.ninja must have an order-only dependency on sub/build.ninja.