Do not attempt to override the intent of DISABLE_MAKE_JOBS, which
does not succeed in any case.

The do-build target does not need to use bash, or even an extra
level of shell.

There are two levels of parallelism in the openoffice build framework.
Split MAKE_JOBS_NUMBER between the two levels instead of potentially
running MAKE_JOBS_NUMBER^2 compilations in parallel.

PR: 199930
Approved by: mat (mentor, implicit)