RFR: 8351323: Parameterize compiler and linker flags for iconv [v3]

[snake66]

> Allows for future support for platforms that require different flags for libiconv support.
> 
> Sponsored-by: The FreeBSD Foundation

snake66 has updated the pull request incrementally with one additional commit since the last revision:

  Unbreak libjdwp build

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/23995/files
  - new: https://git.openjdk.org/jdk/pull/23995/files/d4c4cca5..a9fdfef5

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=23995&range=02
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=23995&range=01-02

  Stats: 2 lines in 1 file changed: 1 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/23995.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/23995/head:pull/23995

PR: https://git.openjdk.org/jdk/pull/23995