Disable the autotools build in PR builds.

We will only build this during the nightly build. It's very rare for the
autotools build to break when the cmake build does not.

.travis.yml

@@ -9,8 +9,8 @@ language: c
 matrix:
   include:
   - stage: "Stage 1"
-    env: JOB=autotools ENV=linux
-    compiler: gcc
+    env: JOB=toxcore ENV=linux
+    compiler: clang
     addons:
       apt: &apt-dependencies
         sources:
@@ -32,8 +32,9 @@ matrix:
         - portaudio19-dev       # For av_test.
         - texinfo               # For libconfig.
   - stage: "Stage 1"
-    env: JOB=toxcore ENV=linux
-    compiler: clang
+    if: type IN (push, api, cron)
+    env: JOB=autotools ENV=linux
+    compiler: gcc
     addons:
       apt: *apt-dependencies
   - stage: "Stage 1"