travis: enable arm/arm64/ppc builds with clang

With the recent patches, criu is finally compileable with
clang for all architectures. To keep it that way, we need
Travis to test that on a regular basis.

The downside is, Travis build time is increased about 2x.

travis-ci: success for travis: enable arm/arm64/ppc builds with clang
Signed-off-by: Kir Kolyshkin <kir@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@virtuozzo.com>

.travis.yml

@@ -11,6 +11,10 @@ env:
   - TR_ARCH=aarch64
   - TR_ARCH=ppc64le
   - TR_ARCH=alpine
+  - TR_ARCH=armv7hf     CLANG=1
+  - TR_ARCH=aarch64     CLANG=1
+  - TR_ARCH=ppc64le     CLANG=1
+  - TR_ARCH=alpine      CLANG=1
 script:
   - sudo make -C scripts/travis $TR_ARCH
 after_success: