One problem though - make succeeded, but 'sudo make install' failed:
...
Making all for bundle Clock...
Copying resources into the bundle wrapper...
make[1]: Leaving directory `/a/mail/GNUMail/GNUMail-build/Bundles/Clock'
Making all for app GNUMail...
plmerge: error while loading shared libraries: libgnustep-base.so.1: cannot
open shared object file: No such file or directory
make[1]: *** [GNUMail.app/Resources/Info-gnustep.plist] Error 127
It's probably because my root GNUstep environment is not OK. Maybe
it would be better for make install to just install and not try to remake?