cmd/link: add runtime.text.N symbols to Mach-O symbol table
On Darwin/ARM64 when external linking, for very large text we
split it into multiple sections. For each section (other than the
first) we create runtime.text.N marker symbols. In CL 316050 I
forgot to add those symbols to the symbol table. This CL does it.
It doesn't actually matter for program execution. But we add them
on ELF when splitting text sections, so we do it here as well.
Also, this makes it easier to tell if we split text sections.
Change-Id: Ida7f8e9431867881e5ee2bc1a2129eeaf83cb878
Reviewed-on: https://go-review.googlesource.com/c/go/+/353209
Trust: Cherry Mui <cherryyz@google.com>
Run-TryBot: Cherry Mui <cherryyz@google.com> Reviewed-by: Than McIntosh <thanm@google.com>