Add osusergo flag to static build
Add osusergo flag to static build

This should fix the following (very legitimate) warnings on static
build:

> /tmp/go-link-818454663/000019.o: In function `mygetgrouplist':
> /usr/lib/go-1.10/src/os/user/getgrouplist_unix.go:15: warning: Using
> 'getgrouplist' in statically linked applications requires at runtime the
> shared libraries from the glibc version used for linking
>
> /tmp/go-link-818454663/000018.o: In function `mygetgrgid_r':
> /usr/lib/go-1.10/src/os/user/cgo_lookup_unix.go:38: warning: Using
> 'getgrgid_r' in statically linked applications requires at runtime the
> shared libraries from the glibc version used for linking
>
> ...

as well as segfaults in the resulting binary.

For more details, check https://github.com/golang/go/issues/23265

Signed-off-by: Kir Kolyshkin <3a017b8ddb3f9cf3e4a59978b004111bdeb97f08@gmail.com>

mikebrow/runc,xiaochenshen/runc,justincormack/runc,opencontainers/runc,dqminh/runc,crosbymichael/runc,rhatdan/runc,mYmNeo/runc,mikebrow/runc,opencontainers/runc,estesp/runc,justincormack/runc,opencontainers/runc,laijs/runc,opencontainers/runc,estesp/runc,adrianreber/runc,mheon/runc,cyphar/runc,mheon/runc,kolyshkin/runc,mikebrow/runc,estesp/runc,mYmNeo/runc,dqminh/runc,kolyshkin/runc,laijs/runc,xiaochenshen/runc,laijs/runc,kolyshkin/runc,rhatdan/runc,crosbymichael/runc,rhatdan/runc,mYmNeo/runc,xiaochenshen/runc,dqminh/runc,kolyshkin/runc,dqminh/runc,adrianreber/runc,justincormack/runc,crosbymichael/runc,rhatdan/runc,adrianreber/runc,cyphar/runc,cyphar/runc,mheon/runc