RFR: JDK-8304684: Memory leak in DirectivesParser::set_option_flag

[Justin King]

Add missing `FREE_C_HEAP_ARRAY` call.

-------------

Commit messages:
 - Fix memory leak in DirectivesParser::set_option_flag

Changes: https://git.openjdk.org/jdk/pull/13125/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=13125&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8304684
  Stats: 4 lines in 1 file changed: 4 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/13125.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/13125/head:pull/13125

PR: https://git.openjdk.org/jdk/pull/13125