Uninstall instructions

[Sjors]

I would be useful to have instructions on which files to remove to fully undo a make install.

[Sjors]

Looking at the install log, something like this:

sudo rm -rf /usr/local/lib/libmultiprocess.a \
/usr/local/include/mp \
/usr/local/bin/mpgen \
/usr/local/include/mp \
/usr/local/include/mpgen.mk \
/usr/local/lib/pkgconfig/libmultiprocess.pc \
/usr/local/lib/cmake/Libmultiprocess

That's a lot of files, so a make uninstall would be easier to use.

[ryanofsky]

It looks like a reasonable way to do this is:

xargs rm -v < build/install_manifest.txt

as described https://stackoverflow.com/questions/41471620/cmake-support-make-uninstall

It'd be probably a good idea to add that command to the documentation in https://github.com/bitcoin-core/libmultiprocess/blob/master/doc/install.md

It would also be possible to add a more portable make uninstall target as described https://gitlab.kitware.com/cmake/community/-/wikis/FAQ#can-i-do-make-uninstall-with-cmake if that is not overkill.

Would welcome opinions about this, or PRs implementing any solution.