We use toStringRef in LLDB in a few places to convert const char* variables to llvm::StringRef.
toStringRef however has no const char* overload (as this is already implemented in the constructor),
so calling toStringRef with a const char will implicitly convert the pointer to true/false, which means
that toStringRef("Hello") will produce the string "true" without any compiler warning.
This patch makes the toStringRef only accept values that are actually bool.