devapp/owners: add owners for build, debug, gccgo, tools, and go/src/cmd/asm
devapp/owners: add owners for build, debug, gccgo, tools, and go/src/cmd/asm

These components have had recent activity in the issue tracker, so
it's helpful to add explicit owners, even if their primary role as
such is to dispatch issues to more-specific owners who are not yet
listed.

Updates golang/go#27586

Change-Id: Ib77b6d1d02b49b9709f1f58797acf2b64ce95e48
Reviewed-on: https://go-review.googlesource.com/c/build/+/172278
Run-TryBot: Bryan C. Mills <1c8aad60184261ccede67f5c63a0d2a3bf3c9ff4@google.com>
TryBot-Result: Gobot Gobot <66cb808b70d30c07676d5e946fee83fd561249e5@golang.org>
Reviewed-by: Brad Fitzpatrick <ae9783c0b0efc69cd85ab025ddd17aa44cdc4aa5@golang.org>

golang/build,golang/build,golang/build,golang/build