Currently, the PGO profile path is global for a single go command
invocation, as it applies to all packages being built (or none).
With -pgo=auto mode with multiple main packages, packages from a
single go command invocation could have different profiles. So it
is necessary that the PGO profile path is per package, which is
this CL does.

For #58099.

Change-Id: I148a15970ec907272db85b4b27ad6b08c41d6c0c
Reviewed-on: https://go-review.googlesource.com/c/go/+/472357
Run-TryBot: Cherry Mui <cherryyz@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Michael Pratt <mpratt@google.com>
Reviewed-by: Bryan Mills <bcmills@google.com>

…nting

In -pgo=auto mode, a package may be built multiple times. E.g. for

go build -pgo=auto cmd/a cmd/b

and both cmd/a and cmd/b imports package p, p may be built twice,
one using a's profile, one using b's. If we need to print p, e.g.
in "go list -deps" or when there is a build failure, p will be
printed twice, and currently we don't distinguish them.

We have a precedence for a similar case: for testing, there is the
original package, and the (internal) test version of the package
(which includes _test.go files). Packages that import the package
under testing may also have two versions (one imports the original,
one imports the testing version). In printing, the go command
distinguishes them by adding a "[p.test]" suffix for the latter,
as they are specifically built for the p.test binary.

We do the similar. When a package needs to be compiled multiple
times for different main packages, we attach the main package's
import path, like "p [cmd/a]" for package p built specifically
for cmd/a.

For #58099.

Change-Id: I4a040cf17e1dceb5ca1810c217f16e734c858ab6
Reviewed-on: https://go-review.googlesource.com/c/go/+/473275
Reviewed-by: Michael Pratt <mpratt@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Run-TryBot: Cherry Mui <cherryyz@google.com>
Reviewed-by: Bryan Mills <bcmills@google.com>

Updates #58099.
Updates #55022.

Change-Id: I32eacdf9f008d16566e0b30230ecc25d110a9811
Reviewed-on: https://go-review.googlesource.com/c/go/+/474236
Run-TryBot: Cherry Mui <cherryyz@google.com>
Reviewed-by: Bryan Mills <bcmills@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Michael Pratt <mpratt@google.com>

Updates #58099.

Change-Id: I95c0397add696f677c86ab7618482e07eb4e9fda
Reviewed-on: https://go-review.googlesource.com/c/go/+/495477
Run-TryBot: Cherry Mui <cherryyz@google.com>
Reviewed-by: Austin Clements <austin@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>