RFR: 8334713: WebKit build failed on LoongArch64 because currentStackPointer is undefined

[Ao Qi]

This problem has been fixed [upstream](https://github.com/WebKit/WebKit/pull/23282). This patch merges the fix in advance.

Error log:


/some_dir/jfx/modules/javafx.web/src/main/native/Source/WTF/wtf/StackPointer.cpp:140:2: error: #error "Unsupported platform: need implementation of currentStackPointer."
  140 | #error "Unsupported platform: need implementation of currentStackPointer."
      | ^~~~~
make[2]: *** [Source/WTF/wtf/CMakeFiles/WTF.dir/build.make:1098: Source/WTF/wtf/CMakeFiles/WTF.dir/StackPointer.cpp.o] Error 1
make[2]: *** Waiting for unfinished jobs....
make[1]: *** [CMakeFiles/Makefile2:360: Source/WTF/wtf/CMakeFiles/WTF.dir/all] Error 2

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

Commit messages:
 - 8334713: WebKit build failed on LoongArch64 because currentStackPointer is undefined

Changes: https://git.openjdk.org/jfx/pull/1482/files
  Webrev: https://webrevs.openjdk.org/?repo=jfx&pr=1482&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8334713
  Stats: 11 lines in 1 file changed: 11 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jfx/pull/1482.diff
  Fetch: git fetch https://git.openjdk.org/jfx.git pull/1482/head:pull/1482

PR: https://git.openjdk.org/jfx/pull/1482