Log Message:
go123: stop requiring /proc on NetBSD

This adds a patch (taken from Go 1.24 development) to use a sysctl
instead of /proc to find the path of the executable, and thus the
files for the standard library.

Earlier versions of Go (including 1.22) had the directory where the
standard library is installed baked in to the binaries as
GOROOT_FINAL. In the interest of portability, this is now determined
at runtime. In NetBSD, this used to use /proc/self/exe, however many
build sandboxes do not have /proc mounted.

With this change, /proc is no longer required for building Go code.