cmd/go: move module build info formatting into runtime/debug
Previously, modload.PackageBuildInfo returned a string containing
information about modules used to build an executable. This string is
embedded in the binary and can be read with debug.ReadBuildInfo or
'go version -m'.
With this change, debug.BuildInfo now has a MarshalText method that
returns a string in the same format as modload.PackageBuildInfo.
Package.load now calls Package.setBuildInfo, which constructs a
debug.BuildInfo, formats it with MarshalText, then sets
Package.Internal.BuildInfo. This is equivalent to what
modload.PackageBuildInfo did.
modload.PackageBuildInfo is deleted, since it's no longer used.
For #37475
Change-Id: I5875a98cb64737637fec2a450ab2ffa7f1805707
Reviewed-on: https://go-review.googlesource.com/c/go/+/353886
Trust: Jay Conrod <jayconrod@google.com>
Run-TryBot: Jay Conrod <jayconrod@google.com> Reviewed-by: Bryan C. Mills <bcmills@google.com>