[dev.link] cmd/link: avoid allsyms loop in initarray setup
In the linker's symtab() function, avoid looping over the context's
Syms.Allsyms array to locate the entry symbol when setting up the init
array section; do an explicit ABI0 symbol lookup instead. This is a
minor efficiency tweak / code cleanup.
Fixes #20205.
Change-Id: I2ebc17a3cb2cd63e9f5052bc80f1b0ac72c960e3
Reviewed-on: https://go-review.googlesource.com/c/go/+/209838
Run-TryBot: Than McIntosh <thanm@google.com> Reviewed-by: Jeremy Faller <jeremy@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>