Run python in the same process as eb

Use `exec` in the `eb` wrapper script to avoid creating a new process.
This allows easier work with e.g. SLURM as signals send to the main process (`eb`) may not be forwarded to Easybuild (python) which results in e.g. stale locks.

Author: Flamefire

eb

@@ -125,4 +125,4 @@ fi
 export EB_SCRIPT_PATH="${0}"
 
 verbose "${PYTHON} -m ${EASYBUILD_MAIN} ${*}"
-"${PYTHON}" -m "${EASYBUILD_MAIN}" "${@}"
+exec "${PYTHON}" -m "${EASYBUILD_MAIN}" "${@}"