Dockerfile: add more packages

These packages are needed for proper build:

* git-core: to get CRIU version (see Makefile)
* pkg-config, libselinux-dev: to check for selinux
  (see criu/Makefile.config)
Signed-off-by: Kir Kolyshkin <kir@openvz.org>
Acked-by: Andrew Vagin <avagin@virtuozzo.com>
Signed-off-by: Pavel Emelyanov <xemul@virtuozzo.com>

scripts/build/Dockerfile.tmpl

@@ -12,7 +12,10 @@ RUN apt-get update && apt-get install -y \
                 libcap-dev \
                 iptables \
                 libnl-3-dev \
-                libcap-dev
+                libcap-dev \
+                libselinux-dev \
+                pkg-config \
+                git-core
 
 COPY . /criu
 WORKDIR /criu