Speed up CI using compiler cache

[nahueespinosa]

Experiment...

[nahueespinosa]

Cache stats:

14.29% hits is unexpectedly low 🤔.

Cache directory:                  /__w/beluga/beluga/.ccache
    Primary config:                   /github/home/.config/ccache/ccache.conf
    Secondary config:                 /etc/ccache.conf
    Stats updated:                    Sun Jan 22 14:31:09 2023
    Stats zeroed:                     Sun Jan 22 14:28:32 2023
    Hits:                                3 /   21 (14.29 %)
      Direct:                            3 /   21 (14.29 %)
      Preprocessed:                      0 /   18 (0.00 %)
    Misses:                             18
      Direct:                           18
      Preprocessed:                     18
    Errors:                              0
    Uncacheable:                         0
  Primary storage:
    Hits:                                6 /   42 (14.29 %)
    Misses:                             36
    Cache size (GB):                  0.02 / 0.50 (4.56 %)
    Files:                             150
  Secondary storage:
    Hits:                                0 /    0 (0.00 %)
    Misses:                              0
    Errors:                              0
    Timeouts:                            0
  Errors:
    Compiler check failed:               0
    Could not find compiler:             0
    Could not write to output file:      0
    Error hashing extra file:            0
    Internal error:                      0
    Missing cache file:                  0
  Uncacheable:
    Autoconf compile/link:               0
    Bad compiler arguments:              0
    Called for linking:                  0
    Called for preprocessing:            0
    Compilation failed:                  0
    Compiler produced empty output:      0
    Compiler produced no output:         0
    Compiler produced stdout:            0
    Could not use modules:               0
    Could not use precompiled header:    0
    Forced recache:                      0
    Multiple source files:               0
    No input file:                       0
    Output to stdout:                    0
    Preprocessing failed:                0
    Unsupported code directive:          0
    Unsupported compiler option:         0
    Unsupported source language:         0

[glpuga]

Cache stats:

14.29% hits is unexpectedly low thinking.

And yet the cache size seems to grow on every run, it's like it fails to match build calls across different jobs.

Maybe the path where the process files are being stored on every run is different; if that's the case this may be related: https://github.com/ccache/ccache/blob/master/doc/MANUAL.adoc#compiling-in-different-directories

[nahueespinosa]

The reason we're getting so many cache misses is that ros-tooling/action-ros-ci performs a checkout of the repository under test inside a subdirectory with a random string prefix.

I think I can hack my way around it, but that's really inconvenient.

[nahueespinosa]

Removing my assignment. I couldn't make ccache work with ros-tooling/action-ros-ci.

Leaving this PR open in case someone wants to take a look. But IMO, the more direct approach would be to replace the external action with colcon commands in the CI pipeline.

[glpuga]

Indeed, action-ros-ci does not seem to be compatible with ccache due to the path randomization it uses.

An alternative is to user industrial_ci, which does support ccache out of the box. It does not support colcon mixins, though, so the coverage arguments would have to be added as straight out CMAKE_ARGS.

I'm not totally sure it's worth it at the current scale of the repo.