add two parameters, privileged and mounts

[Jsky1989]

1. Add priviledged parameter because of "perission denied". The scene is as follows:
   my host enviroment is centos7, selinux mode is enforcing, when use a general account(useid=1001) to cross compile, it appear "perission denied" error, because there is no such account(useid=1001) in docker container enviroment, the owner and group of the mounted folders is 1001, so "perission denied" occurs(This situaion will not appear in ubuntu). There are two kinds of solutions is that start a priviledged container or set the selinux mode to permissive.
2. When compile cgo codes, the g++ flag of LDFLAGS need specify libpath to seach libs, so add mounts parameter to implement user-deined mount directories.

[Jsky1989]

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