MRI scripts cannot handle + in paths, and ubuntu CI makes use of
these.
So we remove the top level build dir from the script and
transform it into a relative path script.
This corrects build failures on ppc64{,le} with the
WITH_EMBEDDED_SERVER option enabled.
MDEV-22641 added an unusual case in which the same object
file in was included twice with a different function
defination. The original cmake/merge_archives_unix.cmake
did not tolerate such eventualities.
So we move to the highest voted answer on Stack Overflow
for the merging of static libraries.
https://stackoverflow.com/questions/3821916/how-to-merge-two-ar-static-libraries-into-one
Thin archives generated compile failures and the libtool
mechanism would of been another dependency and using .la
files that isn't part of a normal cmake output. The straight
Apple mechanism of libtool with static archives also failed
on Linux.
This leaves the MRI script mechansim which was implemented
in this change.
