Bug#864822: firefox: FTBFS: Don't know how to translate powerpc64le-unknown-linux-gnu for rustc

[Aaron M. Ucko]

Source: firefox
Version: 54.0-1
Severity: serious
Tags: upstream
Justification: fails to build from source (but built successfully in the past)

The ppc64el build of firefox failed, apparently because the build
system didn't know how to work with rustc there:

  checking for rustc... /usr/bin/rustc
  checking for cargo... /usr/bin/cargo
  checking rustc version... 1.16.0
  checking cargo version... 0.17.0
  ERROR: Don't know how to translate powerpc64le-unknown-linux-gnu for rustc
  debian/rules:213: recipe for target 'stamps/configure-browser' failed
  make[1]: *** [stamps/configure-browser] Error 1
  make[1]: Leaving directory '/<<PKGBUILDDIR>>'
  debian/rules:358: recipe for target 'build-arch' failed
  make: *** [build-arch] Error 2

Could you please take a look?

Thanks!