When 'go install' is run without arguments in a directory containing a
main package, it deletes an executable file with the same name as the
package (presumably created by 'go build' previously).

'go get' in module mode executes the same code after updating and
downloading modules. However, the special case was misfiring because
we passed an empty list of patterns to InstallPackages.

Fixes #32766

Change-Id: I19aca64ee1fb5a216777dd7d559e8e6a45b3e90c
Reviewed-on: https://go-review.googlesource.com/c/go/+/183846
Run-TryBot: Jay Conrod <jayconrod@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Bryan C. Mills <bcmills@google.com>