.travis.yml: split debug builds

The builds are reaching the magic 50 minute limit with regularity so
lets split them up. Rather than doing a full debug build on both just
enable debug tcg for linux-user.
Signed-off-by: NAlex Bennée <alex.bennee@linaro.org>
Reviewed-by: NRichard Henderson <richard.henderson@linaro.org>

.travis.yml

@@ -86,7 +86,12 @@ matrix:
 
 
     - env:
-        - CONFIG="--enable-debug --enable-debug-tcg"
+        - CONFIG="--enable-debug --enable-debug-tcg --disable-user"
+
+
+    # TCG debug can be run just on it's own and is mostly agnostic to user/softmmu distinctions
+    - env:
+        - CONFIG="--enable-debug-tcg --disable-system"
 
 
     - env: