Disable debug info on CI

This is an attempt to further decrease the cache size on CI.

Author: jtgeibel

.travis.yml

@@ -21,6 +21,7 @@ env:
     - PERCY_PROJECT=crates-io/crates.io
     - PGPORT=5433
     - PATH=$HOME/.cargo/bin:$PATH
+    - RUSTFLAGS="-C debuginfo=0"
 
 install:
   - sudo cp /etc/postgresql/10/main/pg_hba.conf /etc/postgresql/11/main/pg_hba.conf