extension/src/goTest: preserve buildFlags as array when debugging tests

[vrv501]

The debugTestAtCursor CodeLens previously joined go.buildFlags into a
single space-separated string before passing them to the debug adapter.
This corrupted flag values that contain spaces, such as
-ldflags "-X pkg.version=v1.0": after joining, delve sees -X and
pkg.version=v1.0 as separate arguments and fails with "with multiple
packages, -o must refer to a directory or /dev/null".

Meanwhile, the run-test CodeLens passes each flag as a separate
argument to go test, so the same go.buildFlags worked for "run test"
but broke "debug test".

Fix:
Pass buildFlags as an array to startDebugging. The existing
maybeJoinFlags helper in goDebugConfiguration.ts already handles both
shapes: it joins for delve < 1.22.2 and preserves the array for newer
delve, so each element reaches delve as a separate token. Also omit
buildFlags from the debug config when empty to keep behavior parity
with the previous "" sentinel.

Fixes #3933

[gopherbot]

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Patch Set 1:

(1 comment)

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Patch Set 1:

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Message from Vaibhav:

Patch Set 1:

(2 comments)

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[vrv501]

cc: @madelinekalil @h9jiang

[gopherbot]

Message from Madeline Kalil:

Patch Set 2: Commit-Queue+1

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Message from golang-scoped@luci-project-accounts.iam.gserviceaccount.com:

Patch Set 2:

Dry run: CV is trying the patch.

Bot data: {"action":"start","triggered_at":"2026-06-02T14:13:53Z","revision":"42c905443284a104e44d59dd8ab1e7341fa2d268"}

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Message from Madeline Kalil:

Patch Set 2: -Commit-Queue

(Performed by <GERRIT_ACCOUNT_60063> on behalf of <GERRIT_ACCOUNT_3771561>)

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Message from golang-scoped@luci-project-accounts.iam.gserviceaccount.com:

Patch Set 2:

This CL has failed the run. Reason:

Tryjob golang/try/x_vscode-go-go1.25-linux-amd64_docker has failed with summary (view all results):

---

• go on release-branch.go1.25 (commit 917b60b) / vscode-go on master (change 781820)

To reproduce, try gomote repro 8680098898610501809.

Additional links for debugging:

• test github.com/golang/vscode-go module output

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Message from golang-scoped@luci-project-accounts.iam.gserviceaccount.com:

Patch Set 2: LUCI-TryBot-Result-1

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Message from Madeline Kalil:

Patch Set 2:

(1 comment)

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