ascent,ci,olcf: split build and test stage

• It appears that the recurrent error in the Ascent build about missing files is created by a race condition of multiple builds introduced in a recent MR which attempted to optimize the build.

• That change consisted in separating the configure phase in a single job and build/test in another. This caused the race condition since the configure phase sets its source_path which is accessed during the build phase, however, when this happens that path might have been reused by another concurrent machine, erroring in unexpected ways.

• I reverted to the previous way of keeping configure/build in a single stage and test in another one. I also added some desirable changes to to this MR to further tune the build.