Adds the libcall_call_conv setting and use it for libcall calls expansion;

cranelift/codegen/meta/src/shared/settings.rs

@@ -94,6 +94,29 @@ pub fn define() -> SettingGroup {
 
     // Settings specific to the `baldrdash` calling convention.
 
+    settings.add_enum(
+        "libcall_call_conv",
+        r#"
+            Defines the calling convention to use for LibCalls call expansion,
+            since it may be different from the ISA default calling convention.
+
+            The default value is to use the same calling convention as the ISA
+            default calling convention.
+
+            This list should be kept in sync with the list of calling
+            conventions available in isa/call_conv.rs.
+        "#,
+        vec![
+            "isa_default",
+            "fast",
+            "cold",
+            "system_v",
+            "windows_fastcall",
+            "baldrdash",
+            "probestack",
+        ],
+    );
+
     settings.add_num(
         "baldrdash_prologue_words",
         r#"