Constant FLUX_SYSROOT 

pub const FLUX_SYSROOT: &'static str;

Name of the environment variable used to override the Flux sysroot location.

The sysroot is a directory containing flux-driver and precompiled Flux libraries. When unset, the default is ~/.flux (managed by cargo x install). Set this variable to redirect flux and cargo-flux to a different location, e.g., a custom or non-default install path.

During development, cargo x build-sysroot populates <workspace-root>/sysroot/. The test runner (cargo x test) automatically sets FLUX_SYSROOT to that directory so tests use the locally built artifacts instead of ~/.flux.