Fix file flush in 370-dex-v37/build.py

Ensure that file is flushed before we use it.

We have not seen it to cause issues, but in theory it could.

Test: check that build artifacts are same as before
Change-Id: I665756a9b7eae3cb3df826074b7555f3ce1febf5
diff --git a/test/370-dex-v37/build.py b/test/370-dex-v37/build.py
index 8dcba57..1fa6912 100644
--- a/test/370-dex-v37/build.py
+++ b/test/370-dex-v37/build.py
@@ -26,8 +26,8 @@
         f.seek(0)
         f.write(b"dex\n037\x00")
         os.remove("370-dex-v37.jar")
-        cmd = [
-            os.environ["SOONG_ZIP"], "-o", "370-dex-v37.jar", "-f",
-            "classes.dex"
-        ]
-        subprocess.run(cmd, check=True)
+    cmd = [
+        os.environ["SOONG_ZIP"], "-o", "370-dex-v37.jar", "-f",
+        "classes.dex"
+    ]
+    subprocess.run(cmd, check=True)