travis: Move from travis_wait to time-passes

It's looking like we're still timing out all over the place with travis_wait
because the entire `make -j4 rustc-stage1` command is taking too long. Instead,
achieve roughly the same idea by just having `-Z time-passes` printing
information. We shouldn't have a pass that takes longer than 10 minutes in
isolation.

.travis.yml

@@ -41,7 +41,7 @@ script: |
     if [[ $LLVM_VERSION != '3.4' ]]; then exit 0; fi
   fi &&
   make tidy &&
-  travis_wait make -j4 rustc-stage1 &&
+  make -j4 rustc-stage1 RUSTFLAGS='-Z time-passes' &&
   make check-stage1-std check-stage1-rpass check-stage1-cfail check-stage1-rfail check-stage1-doc
 
 env: