Compile error with gcc and ASAN

Attempt to compile against v2022.01.31.00 with gcc-8 and ASAN (`-fsanitize=address -fno-omit-frame-pointer`) results in the following error:

```
include/folly/lang/SafeAssert.h:51:45: error: ‘folly::detail::safe_assert_terminate_w{__folly_detail_safe_assert_arg}’ is not a constant expression
__folly_detail_safe_assert_arg};
^
```

Caused by line `constexpr ::folly::detail::safe_assert_terminate_w

__folly_detail_safe_assert_terminate_w{__folly_detail_safe_assert_arg};`

Use the following app to reproduce:
```
#include

int main() {
FOLLY_SAFE_DCHECK(true);
return 0;
}
```

Start with include/folly/lang/SafeAssert.h at line 51 and compile the minimal application from the issue using gcc-8 with -fsanitize=address and -fno-omit-frame-pointer. Done means the application compiles successfully against v2022.01.31.00 without the constant-expression error.

Written by the indexing model from the issue text.