RFR: 8351323: Parameterize compiler and linker flags for iconv [v2]

[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:

  Set ICONV_* flags for aix and macosx only

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/23995/files
  - new: https://git.openjdk.org/jdk/pull/23995/files/c9382788..d4c4cca5

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=23995&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=23995&range=00-01

  Stats: 28 lines in 4 files changed: 2 ins; 11 del; 15 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