Blank qtdir or kdedir settings cause /bin to be prepended to all PATH entries
kdesrc-build normally sets up the build environment for users by arranging for the Qt and KF5 build platforms to be added to the environment. This is done by prepending into relevant environment variables to ensure that the kdesrc-build-built Qt5 and/or KF5 can override the system's.
If either qtdir or kdedir are left blank, rather than raising an error or assuming the system setup is already correct, we still try to prepend to the build environment with the empty qtdir/kdedir.
This has unpleasant effects for
PATH in particular, since it gets
/bin forcibly introduced at the beginning in this scenario.
See @mwolff's bug report at https://marc.info/?l=kde-core-devel&m=155610926104604&w=2
I have a patch which I will attach or submit an MR for.