Enable gcc caching

riscv-rt/.travis.yml

@@ -29,7 +29,10 @@ install:
 script:
   - ci/script.sh
 
-cache: cargo
+cache:
+  cargo: true
+  directories:
+    - gcc
 
 branches:
   only:

riscv-rt/ci/install.sh

@@ -8,7 +8,7 @@ fi
 
 if [ -n "${CHECK_BLOBS:-}" ]; then
     if [ ! -d gcc/bin ]; then
-        mkdir gcc
+        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