8218997: Xusage text, man help, etc doesn't mention -Xlog option

Reviewed-by: dholmes

src/java.base/share/classes/sun/launcher/resources/launcher.properties

@@ -136,6 +136,9 @@ java.launcher.X.usage=\n\
 \    -Xinternalversion\n\
 \                      displays more detailed JVM version information than the\n\
 \                      -version option\n\
+\    -Xlog:<opts>      Configure or enable logging with the Java Virtual\n\
+\                      Machine (JVM) unified logging framework. Use -Xlog:help\n\
+\                      for details.\n\
 \    -Xloggc:<file>    log GC status to a file with time stamps\n\
 \    -Xmixed           mixed mode execution (default)\n\
 \    -Xmn<size>        sets the initial and maximum size (in bytes) of the heap\n\