Enhanced the <Build_Library> macro to check OBJECTS property in case it's empty

git-svn-id: https://edk2.svn.sourceforge.net/svnroot/edk2/trunk/edk2@2311 6f19259b-4bc3-4df7-8a09-765794883524

Tools/Conf/BuildMacro.xml

@@ -540,6 +540,13 @@ WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
       <var name="FILE_PATH" value="." />
       <mkdir dir="${BIN_DIR}"/>
 
+      <if>
+        <equals arg1="${OBJECTS}" arg2="" trim="true"/>
+        <then>
+          <fail message="No object files"/>
+        </then>
+      </if>
+
       <OnDependency>
         <sourcefiles>
           <fileset dir="${DEST_DIR_OUTPUT}" includes="${OBJECTS}" />