[RISC-V] Disable EnableWriteXorExecute by default on riscv64 architectue (#103408)

* Disable EnableWriteXorExecute by default on riscv64 architectue

On riscv64 architectue any dotnet process that loads corossgened assembly
without DOTNET_EnableWriteXorExecute=0 environment variable set
crashes with "Segmentation fault" error.

For example System.Private.CoreLib.dll is compiled with crossgen2 by default
during build phase so this crash applies to any processes that loads it.

Setting EnableWriteXorExecute=0 disables this options on riscv64 architecure
and prevents these crashes.

Co-authored-by: Dong-Heon Jung <[email protected]>

* Add a link to an issue about re-enabling WriteXorExecute on riscv64 arch.

Co-authored-by: Jan Kotas <[email protected]>

---------

Co-authored-by: Dong-Heon Jung <[email protected]>
Co-authored-by: Jan Kotas <[email protected]>

Author: 3 people

src/coreclr/inc/clrconfigvalues.h

@@ -722,7 +722,12 @@ RETAIL_CONFIG_DWORD_INFO(UNSUPPORTED_LTTng, W("LTTng"), 1, "If DOTNET_LTTng is s
 //
 // Executable code
 //
+// TODO: https://github.com/dotnet/runtime/issues/103465
+#ifdef TARGET_RISCV64
+RETAIL_CONFIG_DWORD_INFO(EXTERNAL_EnableWriteXorExecute, W("EnableWriteXorExecute"), 0, "Enable W^X for executable memory.");
+#else
 RETAIL_CONFIG_DWORD_INFO(EXTERNAL_EnableWriteXorExecute, W("EnableWriteXorExecute"), 1, "Enable W^X for executable memory.");
+#endif // TARGET_RISCV64
 
 #ifdef FEATURE_GDBJIT
 ///