Auto merge of #21594 - gterzian:try_to_fix_travis, r=jdm

Try to fix travis

<!-- Please describe your changes on the following line: -->

---
<!-- Thank you for contributing to Servo! Please replace each `[ ]` by `[X]` when the step is complete, and replace `__` with appropriate data: -->
- [ ] `./mach build -d` does not report any errors
- [ ] `./mach test-tidy` does not report any errors
- [ ] These changes fix #21592 (github issue number if applicable).

<!-- Either: -->
- [ ] There are tests for these changes OR
- [ ] These changes do not require tests because _____

<!-- Also, please make sure that "Allow edits from maintainers" checkbox is checked, so that we can help you if you get stuck somewhere along the way.-->

<!-- Pull requests that do not address these steps are welcome, but they will require additional verification as part of the review process. -->

<!-- Reviewable:start -->
---
This change is [<img src="https://reviewable.io/review_button.svg" height="34" align="absmiddle" alt="Reviewable"/>](https://reviewable.io/reviews/servo/servo/21594)
<!-- Reviewable:end -->

1 files changed, 2 insertions, 0 deletions

diff --git a/.travis.yml b/.travis.yml
index 7483c023ae8..befea629b4e 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -43,6 +43,8 @@ matrix:
       before_cache:
         - ./mach clean-nightlies --keep 2 --force
         - ./mach clean-cargo-cache --keep 2 --force
+        - rm -rf $HOME/.cargo/registry
+        - rm -rf $HOME/.servo/target
       env:
         CC=gcc-6
         CXX=g++-6