travis: remove unneeded debug builds on tags for faster release deployment (#3266)

* add hint

* enable condition for debug

* enable new conditions

.travis.yml

@@ -2,6 +2,8 @@ language: cpp
 
 cache: ccache
 
+conditions: v1
+
 
 matrix:
   fast_finish: true
@@ -10,6 +12,7 @@ matrix:
     dist: trusty
     group: stable
     env: BUILDTYPE=Debug
+    if: tag IS NOT present
   - os: linux
     dist: trusty
     group: stable
@@ -18,6 +21,7 @@ matrix:
   - os: osx
     osx_image: xcode8
     env: BUILDTYPE=Debug
+    if: tag IS NOT present
   - os: osx
     osx_image: xcode8
     env: BUILDTYPE=Release