IMPALA-5207, IMPALA-5214: distcc fixes
enable_distcc should reset IMPALA_DISTCC_ENABLED, otherwise
disable_distcc is not reversible.
Remove the requirement of a toolchain at /opt/Impala-Toolchain. We can
easily identify paths starting with $IMPALA_TOOLCHAIN and remap them in
Did a local build with distcc with IMPALA_TOOLCHAIN at a different
location. Tried toggling disable_distcc and enable_distcc.
Reviewed-by: Tim Armstrong <firstname.lastname@example.org>
Reviewed-by: Matthew Jacobs <email@example.com>
Tested-by: Impala Public Jenkins