gdb links against both libncurses.so and libncursesw.so, but the generation of the latter by sys-libs/ncurses is tied to the "unicode" USE flag. Thus, when using a profile disabling unicode support, gdb fails to execute due to missing libncursesw.so library.
I think that "[unicode]" should be appended to the ncurses line in gdb's RDEPEND in order to force-enable this USE flag for sys-libs/ncurses.
Created attachment 592638 [details, diff]
Comment on attachment 592638 [details, diff]
Sorry, wrong bug.
gdb should not link to libncurses directly is libncursesw is available. You can check it by running 'lddtree /usr/bin/gdb'. If some library dependency doe it then it should be fixed. Typical offender is readline: #669214.