Update ijar tests to verify time stamp.

PiperOrigin-RevId: 185009133

third_party/ijar/test/IjarTests.java

diff --git a/third_party/ijar/test/IjarTests.java b/third_party/ijar/test/IjarTests.java
index d07b37e..4676805 100644
--- a/third_party/ijar/test/IjarTests.java
+++ b/third_party/ijar/test/IjarTests.java
@@ -23,9 +23,11 @@
 import com.google.devtools.build.java.bazel.BazelJavaCompiler;
 import java.io.File;
 import java.io.IOException;
+import java.time.Instant;
 import java.util.Arrays;
 import java.util.Collections;
 import java.util.Enumeration;
+import java.util.GregorianCalendar;
 import java.util.HashMap;
 import java.util.Locale;
 import java.util.Map;
@@ -285,6 +287,9 @@
       Attributes attributes = manifest.getMainAttributes();
       assertThat(attributes.getValue("Target-Label")).isEqualTo("//foo:foo");
       assertThat(attributes.getValue("Injecting-Rule-Kind")).isEqualTo("foo_library");
+      assertThat(jf.getEntry(JarFile.MANIFEST_NAME).getLastModifiedTime().toInstant())
+          .isEqualTo(
+              Instant.ofEpochMilli(new GregorianCalendar(1980, 0, 1, 0, 0, 0).getTimeInMillis()));
     }
   }
 }