sci-electronics/ghdl depends on gnatmake, which is provided by dev-lang/gnat-gcc. Of course ghdl depends on gnat-gcc, but before ghdl can be compiled one has to enter "source /etc/profile" after compiling gnat-gcc. This is why building ghdl right after gnat-gcc fails. If you had gnat-gcc installed already, this is not an issue of course. Reproducible: Always Steps to Reproduce:
For both versions in tree (ghdl-0.27 and 0.29) I cannot reproduce the problem. As 0.26 is gone I am closing the bug. If you observe the problem again for the newer versions please feel free to reopen the bug.