RFR: 8233269: Improve handling of JAVA_ARGS

[Adam Sotona]

LauncherCommon.gmk is unfortunately defining JAVA_ARGS with `-J-ms8m` option for all JDK launchers, including java launcher.
JAVA_ARGS  should not be defined for java launcher (in contrast to the other JDK launchers), and the command line option `-J-ms8m` is obsolete for java launcher.

Proposed patch removes JAVA_ARGS from java launcher, while keeping status quo for all other JDK launchers.
The patch of LauncherCommon.gmk identifies java launcher by undefined MAIN_CLASS.

Thanks for review,
Adam

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Commit messages:
 - 8233269: Improve handling of JAVA_ARGS

Changes: https://git.openjdk.java.net/jdk/pull/8972/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=8972&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8233269
  Stats: 8 lines in 1 file changed: 4 ins; 1 del; 3 mod
  Patch: https://git.openjdk.java.net/jdk/pull/8972.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/8972/head:pull/8972

PR: https://git.openjdk.java.net/jdk/pull/8972