Add test of thread_local! breaking on redefined u8

Author: dtolnay

src/test/ui/thread-local/name-collision.rs

@@ -0,0 +1,15 @@
+// check-pass
+
+#[allow(non_camel_case_types)]
+struct u8;
+
+std::thread_local! {
+    pub static A: i32 = f();
+    pub static B: i32 = const { 0 };
+}
+
+fn f() -> i32 {
+    0
+}
+
+fn main() {}