For Travis CI - tighten up to only upgrade GCC & CMake for 1 CI build.

Test CI builds for all CI mirror branches after clearing the cache. [ccache clear] [ci annotate]

.travis.yml

@@ -43,11 +43,12 @@ matrix:
       compiler: gcc-64bit-static
       env: LINUX=1 URHO3D_LIB_TYPE=STATIC COVERITY_SCAN_THRESHOLD=100 SF_DEFAULT=linux:Linux-64bit-STATIC.tar.gz
     - &Linux-64bit-shared
-      <<: *Linux-64bit
+      addons: {apt: {sources: *default_sources, packages: *linux_packages}}
       compiler: gcc-64bit-shared
       env: LINUX=1 URHO3D_LIB_TYPE=SHARED
-    - <<: *Linux-64bit
+    - <<: *Linux-64bit-shared
       compiler: clang-64bit-static
+      env: LINUX=1 URHO3D_LIB_TYPE=STATIC
     - <<: *Linux-64bit-shared
       compiler: clang-64bit-shared
     - &Linux-32bit