Make all tests in async dir build-pass, adjust implements-fnmut test to begin ICEing during codegen

tests/ui/async-await/async-closures/constrained-but-no-upvars-yet.rs

@@ -1,5 +1,5 @@
 //@ edition: 2021
-//@ check-pass
+//@ build-pass
 //@ revisions: current next
 //@ ignore-compare-mode-next-solver (explicit revisions)
 //@[next] compile-flags: -Znext-solver

tests/ui/async-await/async-closures/force-move-due-to-actually-fnonce.rs

@@ -1,6 +1,6 @@
 //@ aux-build:block-on.rs
 //@ edition:2021
-//@ check-pass
+//@ build-pass
 
 #![feature(async_closure)]
 

tests/ui/async-await/async-closures/force-move-due-to-inferred-kind.rs

@@ -1,6 +1,6 @@
 //@ aux-build:block-on.rs
 //@ edition:2021
-//@ check-pass
+//@ build-pass
 
 #![feature(async_closure)]
 

tests/ui/async-await/async-closures/implements-fnmut.rs

@@ -1,4 +1,4 @@
-//@ check-pass
+//@ build-pass
 //@ edition: 2021
 
 // Demonstrates that an async closure may implement `FnMut` (not just `async FnMut`!)
@@ -9,9 +9,13 @@
 
 #![feature(async_closure)]
 
-fn main() {}
+fn main() {
+    hello(&Ty);
+}
 
-fn needs_fn_mut<T>(x: impl FnMut() -> T) {}
+fn needs_fn_mut<T>(mut x: impl FnMut() -> T) {
+    x();
+}
 
 fn hello(x: &Ty) {
     needs_fn_mut(async || { x.hello(); });

tests/ui/async-await/async-closures/signature-deduction.rs

@@ -1,4 +1,4 @@
-//@ check-pass
+//@ build-pass
 //@ edition: 2021
 
 #![feature(async_closure)]