The linux64 mulet build uses the linux64 mozconfig, but a separate
tooltool manifest. Provide the same rustc there so the mozconfig.rust
inclusion is satisfied.
The patch removes 455 occurrences of FAIL_ON_WARNINGS from moz.build files, and
adds 78 instances of ALLOW_COMPILER_WARNINGS. About half of those 78 are in
code we control and which should be removable with a little effort.
Some mozconfigs don't include mozconfig.linux*, and don't get gtk-related
definitions, so move them in a separate mozconfig. To avoid having two
files, one for 32-bit builds and one for 64-bit builds, rely on the
includer to set PKG_CONFIG_LIBDIR appropriately.
At the same time, move all the --enable-default-toolkit=cairo-gtk2 in that
new file in the case the gtk3 package wasn't pulled from tooltool.
'make check' is somewhat special in that we want to trigger testers
before it finishes. Since moving sendchange into mach is difficult and
'make check' may be going away in the future anyway, just pull it out
for now.
Also remove the MOZ_AUTOMATION_*_SENDCHANGE flags since we aren't using
them.
