[lldb] Don't print to stderr in TypeSystemClang::GetBuiltinTypeForDWARFEncodingAndBitSize

The current code just prints to the System's 'error log' which is usually stderr
(+ some other log backend). Printing to stderr however just interferes with
LLDB's console UI, so when this code is triggered during for example command
completion it just breaks the LLDB console interface until the next redraw.

Instead just use the normal LLDB log which is by default hidden and is what
users usually attach to bug reports.

The only known bug that triggers this is
https://bugs.llvm.org/show_bug.cgi?id=46775

Reviewed By: labath

Differential Revision: https://reviews.llvm.org/D111149