ci: use compiler version in ccache compiler check #24500

compiler_check (CCACHE_COMPILERCHECK) By default, ccache includes the modification time (“mtime”) and size of the compiler in the hash to ensure that results retrieved from the cache are accurate. If compiler plugins are used, these plugins will also be added to the hash. This option can be used to select another strategy.

https://ccache.dev/manual/latest.html#_configuration_options

Since platforms like CI install toolchains on every run, ccache's default option for using mtime causes ccache to not utilize the cache. This PR uses a several years old environment variable to use the version output from the compiler instead.

@div72

Since platforms like CI install toolchains on every run, ccache's default option for using mtime causes ccache to not utilize the cache.

Why do you think so? Logs are ok, for example:

ccache version 4.5.1
Summary:
  Hits:             701 /  703 (99.72 %)
    Direct:         701 /  703 (99.72 %)
    Preprocessed:     0 /    2 (0.00 %)
  Misses:             2
    Direct:           2
    Preprocessed:     2
  Uncacheable:       15
Primary storage:
  Hits:            1403 / 1406 (99.79 %)
  Misses:             3
  Cache size (GB): 0.18 / 0.20 (88.81 %)

@hebasto Extremely low hit rates of https://cirrus-ci.com/task/4649004356075520?logs=ci#L3253 and https://cirrus-ci.com/task/5211954309496832?logs=ci#L2946 irked me but considering other tasks do not share this issue, it's probably unrelated. Closing.

@hebasto Extremely low hit rates of https://cirrus-ci.com/task/4649004356075520?logs=ci#L3253 and https://cirrus-ci.com/task/5211954309496832?logs=ci#L2946 irked me but considering other tasks do not share this issue, it's probably unrelated. Closing.

For macOS cross-compiling builds see #24620.