[llvm] [RISCV] Toggle throttled FP64 feature in SiFive7 scheduling model with subtarget feature (PR #162400)

[LLVM Continuous Integration via llvm-commits]

llvm-ci wrote:

LLVM Buildbot has detected a new failure on builder `flang-x86_64-windows` running on `minipc-ryzen-win` while building `llvm` at step 9 "install-build-unified-treeall".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/166/builds/2850

<details>
<summary>Here is the relevant piece of the build log for the reference</summary>

```
Step 9 (install-build-unified-treeall) failure: build (failure)
...
-- Up-to-date: C:/buildbot/flang-x86_64-windows/flang.install/lib/clangIndexSerialization.lib
-- Up-to-date: C:/buildbot/flang-x86_64-windows/flang.install/lib/clangInstallAPI.lib
-- Up-to-date: C:/buildbot/flang-x86_64-windows/flang.install/lib/clangStaticAnalyzerCore.lib
-- Up-to-date: C:/buildbot/flang-x86_64-windows/flang.install/lib/clangStaticAnalyzerCheckers.lib
-- Up-to-date: C:/buildbot/flang-x86_64-windows/flang.install/lib/clangStaticAnalyzerFrontend.lib
-- Up-to-date: C:/buildbot/flang-x86_64-windows/flang.install/lib/clangFormat.lib
-- Up-to-date: C:/buildbot/flang-x86_64-windows/flang.install/lib/clangInterpreter.lib
-- Up-to-date: C:/buildbot/flang-x86_64-windows/flang.install/lib/clangSupport.lib
-- Installing: C:/buildbot/flang-x86_64-windows/flang.install/bin/diagtool.exe
-- Installing: C:/buildbot/flang-x86_64-windows/flang.install/bin/clang.exe
FAILED: [code=3221225477] CMakeFiles/install.util 
C:\Windows\system32\cmd.exe /C "cd /D C:\buildbot\flang-x86_64-windows\build && "C:\Program Files\CMake\bin\cmake.exe" -P cmake_install.cmake"
ninja: build stopped: subcommand failed.
Cache directory:    C:\Users\buildbot-worker\AppData\Local\ccache
Config file:        C:\Users\buildbot-worker\AppData\Local\ccache\ccache.conf
System config file: C:\ProgramData\ccache\ccache.conf
Stats updated:      10/09/25 18:34:01
Local storage:
  Cache size (GB):    5.0 / 5.0 (100.1%)
  Files:            16721
  Hits:                 0
  Misses:               0
  Reads:                0
  Writes:               0

```

</details>

https://github.com/llvm/llvm-project/pull/162400