[clang] [clang] Fix assertion failure with explicit(bool) in pre-C++11 modes (PR #152985)

[Aaron Ballman via cfe-commits]

================
@@ -0,0 +1,14 @@
+// Regression test for assertion failure when explicit(bool) is used in pre-C++20
+// Fixes GitHub issue #152729
+// RUN: %clang_cc1 -std=c++03 -verify %s
----------------
AaronBallman wrote:

```suggestion
// RUN: %clang_cc1 -std=c++98 -verify %s
// RUN: %clang_cc1 -std=c++03 -verify %s
```
Might as well complete the set.

https://github.com/llvm/llvm-project/pull/152985