Restore Solaris compatibility fixes lost when internal/x/net/lif moved
    to golang.org/x/net/lif.  Also fix the Makefile for x/net/lif and
    x/net/route.
    
    Change x/sys/cpu to get the cache line size from goarch.sh as the
    gofrontend version of internal/cpu does.
    
    Partially based on work by Rainer Orth.
    
    Reviewed-on: https://go-review.googlesource.com/c/gofrontend/+/194438

From-SVN: r275611