The "install" target's dependencies are ordered so that the directories for the bin/docs/slang/locales files are created before those files are installed.
When running with multiple jobs (uncommon during manual install, but some automated build systems do so by default), make doesn't know that the directories have to be created first, so one process may attempt to install the file before the other has finished making the directory.
A simple fix would be to add "installdirs" as a dependency for each of install{bin,docs,slang,locales} in src/Makefile.in . The 'proper' way would probably be to split "installdirs" into multiple targets and add the relevant one of those as a dependency to each install... target.
error output from "make"