Add test for issue-51431

Author: JohnTitor

src/test/ui/asm/issue-51431.rs

@@ -0,0 +1,10 @@
+// ignore-emscripten no asm! support
+
+#![feature(asm)]
+
+fn main() {
+    unsafe {
+        asm! {"mov $0,$1"::"0"("bx"),"1"(0x00)}
+        //~^ ERROR: invalid value for constraint in inline assembly
+    }
+}

src/test/ui/asm/issue-51431.stderr

@@ -0,0 +1,8 @@
+error[E0669]: invalid value for constraint in inline assembly
+  --> $DIR/issue-51431.rs:7:32
+   |
+LL |         asm! {"mov $0,$1"::"0"("bx"),"1"(0x00)}
+   |                                ^^^^
+
+error: aborting due to previous error
+