CI: try to work around build timeouts

- started this morning, but also applies now to yesterday's builds
   when they are restarted. Doesn't seem related to the minor CMake
   change done today.

.travis.yml

@@ -13,7 +13,7 @@ notifications:
     - "chat.freenode.net#calamares"
 
 install:
-  - docker build -t calamares .
+  - travis_wait docker build -t calamares .
 
 script:
   - docker run -v $PWD:/src --tmpfs /build:rw,size=65536k calamares bash -lc "cd /build && cmake -DWEBVIEW_FORCE_WEBKIT=1 -DKDE_INSTALL_USE_QT_SYS_PATHS=ON /src && make -j2 && make install DESTDIR=/build/INSTALL_ROOT"