[PATCH] Hard-coded paths in the source cannot be opt-out

When building mariadb into some un-ordinary directory like /opt/rh (chroot in Software Collections; see softwarecollections.org for details), we do not want to read system paths like /etc/my.cnf.

However, there are several occurrences in the code, where paths are hard-coded in the source and it makes problems to us when building into some chroot, as mentioned above (reading /etc/my.cnf would be wrong, but we specify correct paths using cmake arguments).

Proposed solutions:
Either these cases (hard-coded paths) should be able to opt-out (using e.g. -DNO_HARD_PATHS=1) or they should be removed entirely, since there is always a configured value used.

Another compromise would be to use the hard-coded paths only when the paths are not specified in the cmake call.