try using a new travis staging feature

The idea is to let us avoid building the tools
for each SUITE

.travis.yml

@@ -48,15 +48,19 @@ branches:
     - boom
     - /^hurricane.*$/
 
-install:
-  - make tools verilator -C regression SUITE=none
+jobs:
+  include:
+    - stage: Install Tools
+      install:
+        - make tools verilator -C regression SUITE=none
+      before_install:
+        - export CXX=g++-4.8 CC=gcc-4.8
+      before_cache:
+        - ls -t regression/install | tail -n+2 | sed s@^@regression/install/@ | xargs rm -rf
+    - stage: Test
+      script:
+        - make emulator-ndebug -C regression SUITE=$SUITE
+        - travis_wait 30 make emulator-regression-tests -C regression SUITE=$SUITE
 
-before_install:
-  - export CXX=g++-4.8 CC=gcc-4.8
 
-script:
-  - make emulator-ndebug -C regression SUITE=$SUITE
-  - travis_wait 30 make emulator-regression-tests -C regression SUITE=$SUITE
 
-before_cache:
-  - ls -t regression/install | tail -n+2 | sed s@^@regression/install/@ | xargs rm -rf