Revert "Enable builds against prs"

This reverts commit 5599636.

Author: brson

.travis.yml

@@ -82,7 +82,9 @@ env:
 
 script:
   - >
-      if [ "$TRAVIS_OS_NAME" = "osx" ]; then
+      if [ "$ALLOW_PR" = "" ] && [ "$TRAVIS_BRANCH" != "auto" ]; then
+          echo skipping, not a full build;
+      elif [ "$TRAVIS_OS_NAME" = "osx" ]; then
           travis_retry sh -c 'git submodule deinit -f . && git submodule update --init' &&
           src/ci/run.sh;
       else

appveyor.yml

@@ -130,6 +130,10 @@ cache:
   - "i686-pc-windows-msvc/llvm -> src/rustllvm/llvm-auto-clean-trigger"
   - "x86_64-pc-windows-msvc/llvm -> src/rustllvm/llvm-auto-clean-trigger"
 
+branches:
+  only:
+    - auto
+
 before_deploy:
   - ps: |
         New-Item -Path deploy -ItemType directory