no-copy semantics for function forwarding

```zig
fn foo() Foo {
    return bar();
}
```

```llvm
define internal fastcc void @foo(%Foo* nonnull sret) unnamed_addr #2 !dbg !48 {
Entry:
  call fastcc void @bar(%Foo* sret %0), !dbg !52
  ret void, !dbg !54
}
```

1 files changed, 1 insertions, 1 deletions

diff --git a/src/analyze.cpp b/src/analyze.cpp
index a62c24460e..24c81d2a3f 100644
--- a/src/analyze.cpp
+++ b/src/analyze.cpp
@@ -7278,6 +7278,6 @@ void src_assert(bool ok, AstNode *source_node) {
             buf_ptr(source_node->owner->data.structure.root_struct->path),
             (unsigned)source_node->line + 1, (unsigned)source_node->column + 1);
     }
-    const char *msg = "assertion failed";
+    const char *msg = "assertion failed. This is a bug in the Zig compiler.";
     stage2_panic(msg, strlen(msg));
 }