RFR: 8353632: [Linux] Undefined reference to PlatformSupport::OBSERVED_SETTINGS with C++14 [v2]

[Kevin Rushforth]

> Fixes a link error that occurs when using C++14 to compile and link JavaFX on Linux.
> 
> 
> in function `PlatformSupport::PlatformSupport(JNIEnv_*, _jobject*)':
> PlatformSupport.cpp:90: undefined reference to `PlatformSupport::OBSERVED_SETTINGS'
> 
> 
> The solution, proposed by @johanvos, is to define `PlatformSupport::OBSERVED_SETTINGS` in `PlatformSupport.cpp`.
> 
> I have tested this using gcc 13.2 and 14.2 using C++17 and it builds and runs as expected. Johan has already tested a variant of this on C++14, but I will wait for his explicit review.

Kevin Rushforth has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains two additional commits since the last revision:

 - Merge remote-tracking branch 'upstream/master' into 8353632-PlatformSupport
 - 8353632: [Linux] Undefined reference to PlatformSupport::OBSERVED_SETTINGS with C++14

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

Changes:
  - all: https://git.openjdk.org/jfx/pull/1768/files
  - new: https://git.openjdk.org/jfx/pull/1768/files/43b4eb46..2f3e7f8a

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jfx&pr=1768&range=01
 - incr: https://webrevs.openjdk.org/?repo=jfx&pr=1768&range=00-01

  Stats: 336 lines in 13 files changed: 201 ins; 87 del; 48 mod
  Patch: https://git.openjdk.org/jfx/pull/1768.diff
  Fetch: git fetch https://git.openjdk.org/jfx.git pull/1768/head:pull/1768

PR: https://git.openjdk.org/jfx/pull/1768