RFR: 8292590: Product JVM crashes with FLAG_SET_XXX on non-product Flag

[Ioi Lam]

Please review this trivial fix.

The function `FLAG_MEMBER_SETTER(name)` is no longer declared for non-product flags (`develop` or `notproduct`) in a product build. If you use use `FLAG_SET_XXX` with such a flag in a product build, you'd get a C++ compile error.

This is validated by the change in arguments.cpp, which used to set the `notproduct` flag `UseDebuggerErgo1` in product builds. Now this code must be put inside `#ifndef PRODUCT`

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Commit messages:
 - 8292590: Product JVM crashes with FLAG_SET_XXX on notproduct Flag

Changes: https://git.openjdk.org/jdk/pull/10072/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=10072&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8292590
  Stats: 13 lines in 2 files changed: 12 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/10072.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/10072/head:pull/10072

PR: https://git.openjdk.org/jdk/pull/10072