executor: skip analyze flush broadcast in test binaries

`make bench-daily` (CI job `gobench4`) fails on
`BenchmarkNonPartitionPointGetPlanCacheOn`: `analyze table t` hits
`context deadline exceeded` after 10s. PR #67939 added
`flushStatsDeltaForAnalyze`, which broadcasts FLUSH STATS_DELTA CLUSTER
via a TiDB-type cop request before each ANALYZE. The local-dump
fallback was gated on `intest.InTest`, but that variable is only set
under the `intest` build tag. `make bench-daily` runs `go test`
without the tag, so the broadcast hits the mockstore session's empty
`:10080` and hangs.

Replace the gate with a `runningUnderGoTest` helper backed by
`testing.Testing()`, which the linker sets to true for any binary
produced by `go test` (covering both unit tests and bench-daily) and
leaves false for `go build` of cmd/tidb-server. The gate is therefore
a no-op in production regardless of TOML host configuration, and no
longer depends on the `intest` build tag.

Issue Number: close #68416

Author: 0xPoe

pkg/executor/analyze.go

@@ -24,6 +24,7 @@ import (
 	"slices"
 	"strconv"
 	"strings"
+	"testing"
 	"time"
 
 	"github.com/pingcap/errors"
@@ -89,6 +90,17 @@ const (
 	idxTask
 )
 
+// runningUnderGoTest reports whether the current process is a Go test binary
+// (`go test`, including `make bench-daily`) rather than a real tidb-server
+// produced by `go build` of cmd/tidb-server. Test binaries register in-process
+// TiDB domains without binding a TiDB RPC listener, so a FLUSH STATS_DELTA
+// CLUSTER broadcast would hit a mock ":10080" and burn the TiKV RPC backoff
+// budget before analyze starts. testing.Testing() is set by the linker only
+// for binaries built via `go test`, so the gate is a no-op in production.
+func runningUnderGoTest() bool {
+	return testing.Testing()
+}
+
 // flushStatsDeltaForAnalyze flushes pending stats deltas for the tables whose column-analyze
 // tasks will capture base count / modify_count from mysql.stats_meta. Without this, a stale
 // pre-analyze delta can be applied later and double count rows or modifications.
@@ -101,12 +113,7 @@ func flushStatsDeltaForAnalyze(ctx context.Context, sctx sessionctx.Context, pla
 		return err
 	}
 
-	// HACK: Some tests register in-process TiDB domains but do not start TiDB RPC
-	// endpoints. Broadcasting FLUSH STATS_DELTA CLUSTER to those mock endpoints can
-	// spend the TiKV RPC backoff budget before analyze really starts. When the test
-	// topology cannot receive TiDB broadcast requests, dumping local deltas is the
-	// only viable approximation.
-	if intest.InTest {
+	if runningUnderGoTest() {
 		flushedLocally, err := flushAnalyzeStatsDeltaForTest(ctx, sctx, plan)
 		if err != nil {
 			return err