Fix flaky spill test (facebookincubator#10629)

Summary:
Fast machines might be able to make each write in sub-microsecond, recorded as 0us in each stats addition. This may result in the total write time to be 0us. Loose the condition to make the test non-flaky.

Pull Request resolved: facebookincubator#10629

Reviewed By: kevinwilfong

Differential Revision: D60551759

Pulled By: tanjialiang

fbshipit-source-id: 0c1fdc93759844ad42969827aa96e38cbc2ed48d

Author: tanjialiang

velox/exec/tests/SpillTest.cpp

@@ -291,7 +291,9 @@ class SpillTest : public ::testing::TestWithParam<common::CompressionKind>,
     ASSERT_EQ(stats.spilledFiles, expectedNumSpilledFiles);
     ASSERT_GT(stats.spilledBytes, 0);
     ASSERT_GT(stats.spillWrites, 0);
-    ASSERT_GT(stats.spillWriteTimeUs, 0);
+    // NOTE: On fast machines we might have sub-microsecond in each write,
+    // resulting in 0us total write time.
+    ASSERT_GE(stats.spillWriteTimeUs, 0);
     ASSERT_GE(stats.spillFlushTimeUs, 0);
     ASSERT_GT(stats.spilledRows, 0);
     // NOTE: the following stats are not collected by spill state.