Enable gcc caching

.travis.yml

@@ -21,7 +21,8 @@ matrix:
       if: (branch = staging OR branch = trying OR branch = master) OR (type = pull_request AND branch = master)
 
     - env: CHECK_BLOBS=1
-      rust: stable
+      rust:
+      language: bash
       if: (branch = staging OR branch = trying OR branch = master) OR (type = pull_request AND branch = master)
 
 
@@ -32,7 +33,10 @@ script:
   - ci/script.sh
 
 
-cache: cargo
+cache:
+  cargo: true
+  directories:
+    - gcc
 before_cache:
   # Travis can't cache files that are not readable by "others"
   - chmod -R a+r $HOME/.cargo

ci/install.sh

@@ -7,6 +7,8 @@ if [ -n "${TARGET:-}" ]; then
 fi
 
 if [ -n "${CHECK_BLOBS:-}" ]; then
-    mkdir gcc
+    if [ ! -d gcc/bin ]; then
+        mkdir -p gcc
         curl -L https://static.dev.sifive.com/dev-tools/riscv64-unknown-elf-gcc-8.1.0-2018.12.0-x86_64-linux-ubuntu14.tar.gz | tar --strip-components=1 -C gcc -xz
+    fi
 fi