As alerted via https://github.com/gentoo/gentoo/pull/2891 . More investigation is required but it would seem that the mozilla build system isn't honouring the SHELL it detects at configure time. This should likely be fixed via a build system patch rather than an override?
Created attachment 454712 [details] build.log So I'm running into this bug with mksh as /bin/sh. This is with www-client/firefox-50.0.1 I attached the build.
Created attachment 455288 [details] ff.build.50.0.2.log same thing with 50.0.2
Same thing with: firefox-50.1.0 It worked by forcing SHELL to bash on emake install, do you want me to submit that patch again?
commit 61fe4f891af6a622ebb4a3754f07ac5a54f5c629 Author: Ian Stakenvicius <axs@gentoo.org> Date: Fri Jan 27 11:03:08 2017 -0500 www-client/firefox: adjust SHELL, other var specs on calls to emake Aligned the use of forcing various variables on calls to emake, so that they are common across all current versions of firefox. This should address two bugs related to SHELL: bug 602370 and bug 600488 Package-Manager: portage-2.3.0 Note, this commit only adjusted firefox-45.7 and firefox-51, as previous versions are or will shortly be removed from the gentoo repo.