RFR: 8373122: JFR build failure with CDS disabled due to -Werror=unused-function after JDK-8365400 [v2]

[Hao Sun]

> `get_source(const AOTClassLocation* cl, JavaThread* jt)` is only used by `JfrClassDefineEvent::on_restoration()` within an `INCLUDE_CDS` guard.
> 
> Add the same `INCLUDE_CDS` guard to mitigate the GCC warning.
> 
> Tests: JDK build with CDS disabled passed on both x86_64 and aarch64.
>        tier1~3 passed on both x86_64 and aarch64.

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

  Move down the helper to avoid introducing new conditions
  
  Address mgronlun's comment

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/28917/files
  - new: https://git.openjdk.org/jdk/pull/28917/files/c1cbc737..bccc9eac

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=28917&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=28917&range=00-01

  Stats: 30 lines in 1 file changed: 14 ins; 16 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/28917.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/28917/head:pull/28917

PR: https://git.openjdk.org/jdk/pull/28917