Aarch64 fenix rust cross-compilation fails

While building fenix-rust-android-aarch64:

  = note: /var/tmp/build/rustc-1.43.0-src/build/build/x86_64-unknown-linux-gnu/stage2-std/armv7-linux-androideabi/release/deps/std-0c290f22c43402b2.std.e84jh5q4-cgu.0.rcgu.o: error adding symbols: File in wrong format
          clang: error: linker command failed with exit code 1 (use -v to see invocation)


error: aborting due to previous error

error: could not compile `std`.

To learn more, run the command again with --verbose.
command did not execute successfully: "/var/tmp/dist/fenix-rust-rust-old/bin/cargo" "build" "-Zconfig-profile" "--target" "armv7-linux-androideabi" "-Zbinary-dep-depinfo" "-j" "8" "--release" "--frozen" "--features" "panic-unwind backtrace compiler-builtins-c" "--manifest-path" "/var/tmp/build/rustc-1.43.0-src/src/libtest/Cargo.toml" "--message-format" "json-render-diagnostics"                           
expected success, got: exit code: 101
failed to run: /var/tmp/build/rustc-1.43.0-src/build/build/bootstrap/debug/bootstrap build

And, this seems to be a result of a mismatch in the configured toolchain (in the container's build script):

mkdir build
cd build
../configure --prefix=$distdir --enable-local-rust --enable-vendor --enable-extended --release-channel=stable --sysconfdir=etc --target=armv7-linux-androideabi --set=target.armv7-linux-androideabi.cc=aarch64-linux-android21-clang --set=target.armv7-linux-androideabi.ar=aarch64-linux-android-ar

We should be building for aarch64, but we're targetting armv7 and using the aarch64 toolchain.