Bug#930012: gcc-8: ICE building firefox 68.0~b6-2 on s390x and i386

[Olivier Tilloy <olivier.tilloy@canonical.com>]

Ubuntu is also affected (all supported releases, from 16.04 to 19.10, builds are being done in https://launchpad.net/~mozillateam/+archive/ubuntu/firefox-next/+packages).

I don't have a workaround, but here are some data points:

 - builds on 16.04 exhibit the same problem, this is with GCC 6.4.0

 - https://skia.googlesource.com/skcms/+/7362d88 is the change in skcms (a skia subproject) that triggers the build error, it is the commit immediately after the version that's in firefox 67 source tarballs

 - reverting skcms to the version in the 67 source tarballs (revision dfd5b3a) makes the build succeed, with no apparent functional issues (tested on i386)

 - for reference, this is the range of new skcms revisions in the firefox 68 source tarballs: https://skia.googlesource.com/skcms/+log/dfd5b3a..5e67e5c