Container options

For jobs that run a lot of configure scripts a lot of performance could be gained by having `/tmp` or `TMPDIR` on a ramdisk. **Describe the solution you'd like** A way to inject `docker run` parameters for the container start as a replacement for what we otherwise have in `/etc/gitlab-runner/gitlab-runner.toml` **Describe alternatives you've considered** I haven't figured out any alternative since (as far as I understand) it can't be solved from within the job.. **Additional context** for context, I'm looking at tuning a basic chain of builds for a buildroot based OS+bootloader build. Some of the time is spent in actual CC build time, some good bit in downloads. I've started caching the apt downloads and added a proxy for the rest, added ccache and preserve the CCACHE_DIR. It's cut things down from 28 to 21 minutes with CCACHE and apt will save another, proxy maybe another, but I feel most of the time is in configure runs, and I know from, well, from the last 25 years that a ramdisk / tmpfs drive for configures 1000s of tiny test scripts saves a lot of time. That's how I ended up loooking into this.