Simplify BuildTest.StatFailureAbortsBuild test case

Remove a dependency cycle from the test case, as cycles are covered by
other tests.  Ensure this case covers stat failure on a valid graph.
diff --git a/src/build_test.cc b/src/build_test.cc
index 623ed14..8c9fb11 100644
--- a/src/build_test.cc
+++ b/src/build_test.cc
@@ -1747,8 +1747,8 @@
 TEST_F(BuildTest, StatFailureAbortsBuild) {
   const string kTooLongToStat(400, 'i');
   ASSERT_NO_FATAL_FAILURE(AssertParse(&state_,
-("build " + kTooLongToStat + ": cat " + kTooLongToStat + "\n").c_str()));
-  // Also cyclic, for good measure.
+("build " + kTooLongToStat + ": cat in\n").c_str()));
+  fs_.Create("in", "");
 
   // This simulates a stat failure:
   fs_.files_[kTooLongToStat].mtime = -1;