cmd/dist: convert most remaining tests to use goTest
This converts most of the remaining manual "go test" command line
construction in cmd/dist to use the goTest abstraction and
registerTest.
At this point, the only remaining place that directly constructs go
test command lines is runHostTest.
This fixes a bug in the "nolibgcc:os/user" test. It was clearly
supposed to pass "-run=^Test[^CS]", but the logic to override the
"-run" flag for "nolibgcc:net" caused "nolibgcc:os/user" to pass
*both* "-run=^Test[^CS]" and "-run=". This was then rewritten into
just "-run=" by flattenCmdline, which caused all os/user tests to run,
and not actually skip the expensive tests as intended. (This is a
great example of why the new abstraction is much more robust than
command line construction.)
I traced all exec calls from cmd/dist on linux/amd64 and, other than
the fix to nolibgcc:os/user, this makes only no-op changes (such as
re-arranging the order of flags).
For #37486.
Change-Id: Ie8546bacc56640ea39f2804a87795c14a3fe4c7d
Reviewed-on: https://go-review.googlesource.com/c/go/+/450018
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
Run-TryBot: Austin Clements <austin@google.com>
Reviewed-by: Dmitri Shuralyov <dmitshur@golang.org>