Correctly emit spv extension targeting EXT rather than NV, added to test for this case (#3864)

CullPrimitive [follows capabilities to emit as per SPIR-V specification](https://registry.khronos.org/SPIR-V/specs/unified1/SPIRV.html#_capability)

1 files changed, 1 insertions, 1 deletions

diff --git a/source/slang/slang-emit-spirv.cpp b/source/slang/slang-emit-spirv.cpp
index ae7c9bcc8..36c9aa5f8 100644
--- a/source/slang/slang-emit-spirv.cpp
+++ b/source/slang/slang-emit-spirv.cpp
@@ -3815,7 +3815,7 @@ struct SPIRVEmitContext
                 else if (semanticName == "sv_cullprimitive")
                 {
                     requireSPIRVCapability(SpvCapabilityMeshShadingEXT);
-                    ensureExtensionDeclaration(UnownedStringSlice("SPV_NV_mesh_shader"));
+                    ensureExtensionDeclaration(UnownedStringSlice("SPV_EXT_mesh_shader"));
                     return getBuiltinGlobalVar(inst->getFullType(), SpvBuiltInCullPrimitiveEXT);
                 }
                 else if (semanticName == "sv_shadingrate")