travis.yml: reduce scope of the --enable-debug build

Adding debug makes things run a bit slower so lets not hammer all the
targets.
Signed-off-by: NAlex Bennée <alex.bennee@linaro.org>
Reviewed-by: NPhilippe Mathieu-Daudé <philmd@redhat.com>

.travis.yml

@@ -124,12 +124,13 @@ matrix:
         - CACHE_NAME="${TRAVIS_BRANCH}-linux-gcc-default"
 
 
+    # --enable-debug implies --enable-debug-tcg, also runs quite a bit slower
     - env:
-        - CONFIG="--enable-debug --enable-debug-tcg --disable-user"
+        - CONFIG="--enable-debug --target-list=${MAIN_SOFTMMU_TARGETS}"
         - CACHE_NAME="${TRAVIS_BRANCH}-linux-gcc-debug"
 
 
-    # TCG debug can be run just on it's own and is mostly agnostic to user/softmmu distinctions
+    # TCG debug can be run just on its own and is mostly agnostic to user/softmmu distinctions
     - env:
         - CONFIG="--enable-debug-tcg --disable-system"
         - CACHE_NAME="${TRAVIS_BRANCH}-linux-gcc-debug"