Restore some of the fixes that were applied to golang_org/x/net/lif
    but were lost when 1.12 moved the directory to internal/x/net/lif.
    
    Add support for reading /proc to fetch argc/argv/env for c-archive mode.
    
    Reviewed-on: https://go-review.googlesource.com/c/158640

From-SVN: r268130