This will enable test sharding over multiple VMs, to speed trybot answers.

Update #10029

Change-Id: Ie277c6459bc38005e4d6af14d22effeaa0a4667e
Reviewed-on: https://go-review.googlesource.com/6531
Reviewed-by: Russ Cox <rsc@golang.org>
Reviewed-by: Alex Brainman <alex.brainman@gmail.com>

Make all-compiler a trybot-only builder. This will be used for
temporary sharded ARM trybots.

Updates golang/go#10029

Change-Id: I6cc3188887c2f24edef97d0a9354e39553a15896
Reviewed-on: https://go-review.googlesource.com/10051
Reviewed-by: Andrew Gerrand <adg@golang.org>

For upcoming sharded ARM builders.

Updates #10029

Change-Id: I3b1df9560be697c514a8ced0462814d406e23132
Reviewed-on: https://go-review.googlesource.com/10055
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

This is a quick & hacky version of our eventual sharding plan.  Later
we want to run make.bash once, snapshot it, and then intelligently
schedule all the tests out over N machines (starting with the built
snapshot), giving each the next test to run as they become idle.
And then we want to stitch together all of their output.

But this CL just makes 6 ARM builders, each of which runs make.bash (4
minutes) and then each which runs a statically-configured subset of
the tests. Based on measurements, each should run between 8.2 and 10.6
minutes. We can break up some of the larger test cases later into more
shardable pieces (in particular: "test").

Update golang/go#10029

Change-Id: Ib3e008b61ce6f28d799ae298c8467bf62d89e5d4
Reviewed-on: https://go-review.googlesource.com/10056
Reviewed-by: Andrew Gerrand <adg@golang.org>

…fter test

Otherwise subsequent tests won't see any modified GOROOT.

With this CL I can move my GOROOT, set GOROOT to the new location, and
the runtime tests pass. Previously the crash_tests would instead look
for the GOROOT baked into the binary, instead of the env var:

--- FAIL: TestGcSys (0.01s)
        crash_test.go:92: building source: exit status 2
                go: cannot find GOROOT directory: /home/bradfitz/go
--- FAIL: TestGCFairness (0.01s)
        crash_test.go:92: building source: exit status 2
                go: cannot find GOROOT directory: /home/bradfitz/go
--- FAIL: TestGdbPython (0.07s)
        runtime-gdb_test.go:64: building source exit status 2
                go: cannot find GOROOT directory: /home/bradfitz/go
--- FAIL: TestLargeStringConcat (0.01s)
        crash_test.go:92: building source: exit status 2
                go: cannot find GOROOT directory: /home/bradfitz/go

Update #10029

Change-Id: If91be0f04d3acdcf39a9e773a4e7905a446bc477
Reviewed-on: https://go-review.googlesource.com/10685
Reviewed-by: Andrew Gerrand <adg@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>

Also modifies 'dist test' to use that sharding, and removes some old
temporary stuff from dist test which are no longer required.

'dist test' now also supports running a list of tests given in
arguments, mutually exclusive with the existing -run=REGEXP flag. The
hacky fast paths for avoiding the 1 second "go list" latency are now
removed and only apply to the case where partial tests are run via
args, instead of regex.  The build coordinator will use both styles
for awhile. (the statically-sharded ARM builders on scaleway will
continue to use regexps, but the dynamically-shared builders on GCE
will use the list of tests)

Updates #10029

Change-Id: I557800a54dfa6f3b5100ef4c26fe397ba5189813
Reviewed-on: https://go-review.googlesource.com/10688
Reviewed-by: Andrew Gerrand <adg@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>