The actual fix as been done by "pkglint -F */*/buildlink3.mk", and was
reviewed manually.
There are some .include lines that still are indented with zero spaces
although the surrounding .if is indented. This is existing practice.
Go packages now define a set of files to buildlink in their buildlink3.mk.
go-packages.mk no longer looks in ${PREFIX}/gopkg during the build. This
should also fix the spurious issues with rebuilds of .a files during bulk
builds of Go packages.