cmd/go: decide whether to install .a based on number of CgoFiles
Instead of hardcoding the set of five packages that depend on cgo to
decide whether a package should have an install target, make the
decision based on whether the package has any CgoFiles. This means that
in nocgo configurations, there will be no installed packages, and that
if an GOOS/GOARCH combination doesn't have cgo files we don't
unnecessarily install a .a.
Because the determination of whether a file is a CgoFile is made later
in the Import functions, the choice of whether to add a PkgObj for teh
case there are CgoFiles is moved later. One concern here is that in some
cases, PkgObj may be set differently in the case of the FindOnly mode,
since the determination is moved across the boundary. We might want
to always set PkgObj after the FindOnly boundary for consistency? cmd/go
doesn't seem to use it when calling Import with FindOnly.
Also remove internal/buildinternal/needs_install.go because we will be
checking whether to install based on the number of cgo files and it
might be overkill to make the NeedsInstalledDotA function be the
equivalent of len(input) > 0.
For #47257
Change-Id: I5f7f2137dc99aaeb2e2695c14e0222093a6b2407
Reviewed-on: https://go-review.googlesource.com/c/go/+/448803 Reviewed-by: Bryan Mills <bcmills@google.com> Reviewed-by: Michael Matloob <matloob@golang.org>
TryBot-Result: Gopher Robot <gobot@golang.org>
Run-TryBot: Michael Matloob <matloob@golang.org>