Travis: Skip offline rust builds for Linux gcc

We already do an online rust build for Linux gcc.

Part of 27252.

.travis.yml

@@ -81,6 +81,12 @@ matrix:
     - compiler: gcc
       os: linux
       env:
+    ## offline rust builds for gcc on Linux are redundant, because we do an
+    ## online rust build for gcc on Linux
+    - compiler: gcc
+      os: linux
+      ## TOR_RUST_DEPENDENCIES is spelt RUST_DEPENDENCIES in 0.3.2
+      env: RUST_OPTIONS="--enable-rust" RUST_DEPENDENCIES=true HARDENING_OPTIONS=""
 
 ## We don't need sudo. (The "apt:" stanza after this allows us to not need
 ## sudo; otherwise, we would need it for getting dependencies.)

changes/ticket27252-032

@@ -1,3 +1,5 @@
   o Minor features (continuous integration):
     - Only run one online rust build in Travis, to reduce network errors.
+      Skip offline rust builds on Travis for Linux gcc, because they're
+      redundant.
       Implements ticket 27252.