travis: add a docker file to build on Alpine Linux

Signed-off-by: Andrew Vagin <avagin@virtuozzo.com>
Signed-off-by: Pavel Emelyanov <xemul@virtuozzo.com>

scripts/build/Dockerfile.alpine

+FROM alpine:3.4
+RUN apk update && apk add \
+                build-base \
+                protobuf-c-dev \
+                protobuf-dev \
+                python \
+                libaio-dev \
+                libcap-dev \
+                libnl3-dev \
+                pkgconfig
+COPY . /criu
+WORKDIR /criu
+RUN make clean && make -j $(nproc)

scripts/build/Makefile

@@ -11,6 +11,9 @@ binfmt_misc:
 	./binfmt_misc
 .PHONY: binfmt_misc
 
+alpine:
+	docker build  -t criu-$@ -f Dockerfile.alpine ../..
+
 %: Dockerfile.% qemu-user-static binfmt_misc
 	docker build  -t criu-$@ -f $< ../..