cmd/go: add error for cross-compiled -race builds

[keyan]

Race builds require C dependencies, but cross-compiled cgo builds are
not always possible, so don't suggest enabling CGO in those cases.

Fixes #37021

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Message from Keyan Pishdadian:

Patch Set 1:

I'm happy to add some sort of test for this, but I couldn't manage to find if there are existing test for this path.

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Message from Ian Lance Taylor:

Patch Set 1:

(2 comments)

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Message from Bryan C. Mills:

Patch Set 1:

(1 comment)

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Message from Keyan Pishdadian:

Patch Set 2:

Sorry, I've rebased my commit https://github.com/keyan/go/commit/cbf43c1bbb0f209474cc323b3813cf270a2ba0a8, but I'm still trying to get the hang of gerrit.

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Message from Abbigale Edmondson:

Patch Set 2:

thanks he found out he aint stupid

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Message from Bryan C. Mills:

Patch Set 2: Run-TryBot+1 Code-Review+2

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Message from Gobot Gobot:

Patch Set 2:

TryBots beginning. Status page: https://farmer.golang.org/try?commit=d2fa7a84

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Message from Bryan C. Mills:

Patch Set 2:

Patch Set 2:

thanks he found out he aint stupid

I'm not sure where this comment came from, but this is comment is not in line with our Gopher values (https://golang.org/conduct#values). We aim to be friendly and welcoming, especially to new contributors.

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Patch Set 2: TryBot-Result+1

TryBots are happy.

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Message from Bryan C. Mills:

Patch Set 2:

Patch Set 2:

Sorry, I've rebased my commit https://github.com/keyan/go/commit/cbf43c1bbb0f209474cc323b3813cf270a2ba0a8, but I'm still trying to get the hang of gerrit.

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Message from Keyan Pishdadian:

Patch Set 3:

Patch Set 2:

Patch Set 2:

Sorry, I've rebased my commit https://github.com/keyan/go/commit/cbf43c1bbb0f209474cc323b3813cf270a2ba0a8, but I'm still trying to get the hang of gerrit.

To edit the Gerrit commit message, edit the PR description and first comment on GitHub. (They're sync'd across automatically; see the bulleted list at the end of https://golang.org/doc/contribute.html#sending_a_change_github.)

Gotcha, thanks Bryan. Thankfully I figured out the Gerrit workflow and will use it directly for future CLs.

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This PR is being closed because golang.org/cl/230202 has been merged.