Now that cmake requires out-of-tree builds, it would be nice to unify the -logsourcelocations output format.

Currently, with cmake, it includes the src, which seems redundant and doesn't match the guix builds.

Out-of-tree builds were always broken in this regard, but now would probably be a good time to unify it to drop the src prefix in logsourcelocations, so that it matches: (1) legacy-autotools-in-tree behavior (2) legacy- and cmake-guix build behavior.

Ref:

$ ./bld-cmake/src/bitcoind -printtoconsole -logsourcelocations -asmap=/tmp/no_file 
2024-08-23T08:29:32Z [init] [src/init/common.cpp:149] [LogPackageVersion] Bitcoin Core version v27.99.0-41051290ab3b-dirty (release build)

(In all guix builds it would be [init/common.cpp:149])

This should be possible by applying the appropriate prefix-map, which currently is only applied in guix and when compiling with ccache.