travis ppc64: use ubuntu zesty

This comes with newer libc headers so we can catch errors earlier.
Also, clang 4.0.
Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>
Signed-off-by: Andrei Vagin <avagin@virtuozzo.com>

scripts/build/Dockerfile.ppc64le.hdr

-FROM ppc64le/ubuntu:trusty
+FROM ppc64le/ubuntu:zesty
 
 ENV QEMU_CPU POWER8
 COPY scripts/build/qemu-user-static/usr/bin/qemu-ppc64le-static /usr/bin/qemu-ppc64le-static

scripts/build/Makefile

@@ -41,6 +41,7 @@ $(foreach t,$(TARGETS),$(eval $(call CLANG_DEP,$(t))))
 %-clang:	DB_ENV=--build-arg ENV1=CCACHE_CPP2
 alpine-clang:	DB_CC=--build-arg CC=clang
 aarch64-clang:	DB_CC=--build-arg CC=clang
+ppc64le-clang:	DB_CC=--build-arg CC=clang
 .PHONY: $(TARGETS_CLANG)
 
 clean: