pin all the targets to nightly-2016-12-05

.travis.yml

@@ -1,7 +1,8 @@
 cache: cargo
 dist: trusty
 language: rust
-rust: nightly
+# NOTE(nightly-2016-12-05) work around for rust-lang/rust#38281
+rust: nightly-2016-12-05
 services: docker
 sudo: required
 
@@ -22,15 +23,10 @@ matrix:
     - env: TARGET=powerpc-unknown-linux-gnu
     - env: TARGET=powerpc64-unknown-linux-gnu
     - env: TARGET=powerpc64le-unknown-linux-gnu
-    # NOTE(nightly-2016-12-05) work around for rust-lang/rust#38281
     - env: TARGET=thumbv6m-none-eabi
-      rust: nightly-2016-12-05
     - env: TARGET=thumbv7em-none-eabi
-      rust: nightly-2016-12-05
     - env: TARGET=thumbv7em-none-eabihf
-      rust: nightly-2016-12-05
     - env: TARGET=thumbv7m-none-eabi
-      rust: nightly-2016-12-05
     - env: TARGET=x86_64-apple-darwin
       os: osx
 env: TARGET=x86_64-unknown-linux-gnu