env/linux-x86-std: add libraries required by x/mobile subrepo.

Change-Id: Ib33f9875354ab2d74700f8d213b01c013beee2d5
Reviewed-on: https://go-review.googlesource.com/12891
Reviewed-by: Andrew Gerrand <[email protected]>

Author: hyangah

env/linux-x86-std/Dockerfile

@@ -29,6 +29,9 @@ RUN apt-get install -y --no-install-recommends net-tools ifupdown isc-dhcp-clien
 # And misc basic tools:
 RUN apt-get install -y --no-install-recommends procps lsof psmisc
 
+# Required by x/mobile repo:
+RUN apt-get install -y --no-install-recommends libgles2-mesa-dev libopenal-dev fonts-droid
+
 RUN apt-get clean
 
 RUN mkdir -p /go1.4-amd64 && (curl --silent https://storage.googleapis.com/golang/go1.4.linux-amd64.tar.gz | tar -C /go1.4-amd64 -zxv)