libgo: Solaris and x/sys/cpu compatibility fixes

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.

Change-Id: Ic4df65b1b2c7823a53b5d6e7285666c22c42132a
Reviewed-on: https://go-review.googlesource.com/c/gofrontend/+/194438
Reviewed-by: Than McIntosh <thanm@google.com>
Reviewed-by: Cherry Zhang <cherryyz@google.com>
15 files changed