Speedup HIP builds
With newer ROCm it seems that we do not have to build the whole project with the ROCm clang.
- It builds VTK-m hip source files with -O0 to dramatically reduce build times.
- This MR enables HIP build (not test job) to be triggered automatically in every merge-request the build time is <30mins with a cold cache <1 min with hot cache.
- It keeps HIP jobs from running in merge-requests since sometime they take about an hour to complete.
Edited by Vicente Bolea