Add missing error test

Author: arsenm

llvm/test/Transforms/RewriteStatepointsForGC/unsupported-gc-error.ll

@@ -0,0 +1,12 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
+; RUN: not --crash opt -disable-output -passes=rewrite-statepoints-for-gc %s 2>&1 | FileCheck %s
+
+; CHECK: LLVM ERROR: unsupported GC: unsupported-gc
+
+declare void @g()
+declare i32 @h()
+
+define ptr addrspace(1) @f0(ptr addrspace(1) %arg) gc "unsupported-gc" {
+  call void @g() [ "deopt"(i32 100) ]
+  ret ptr addrspace(1) %arg
+}