internal/pkgbits: change EnableSync into a dynamic knob
Rather than requiring users to recompile the compiler and all tools to
enable/disable sync markers, this CL adds a flag word into the Unified
IR file format to allow indicating whether they're enabled or not.
This in turn requires bumping the file format version.
Thanks to drchase@ for benchmarks showing this isn't as expensive as I
feared it would be.
Change-Id: I99afa0ee0b6ef5f30ed8ca840805ff9fd46b1857
Reviewed-on: https://go-review.googlesource.com/c/go/+/417097 Reviewed-by: David Chase <drchase@google.com>
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>