For the bug 11740:
If there is already debug info in the assembly file, and user hope to use -g option for
compiling, we think we should not directly report an error.
According to what GNU assembler did, it just reused the debug info in the assembly file,
and turned off the DEBUG_TYPE option so that there will be no new debug info emitted
by assembler. This fix is just as what GNU assembler did.
The concern is the situation that there are two .text sections in the assembly file, one with
debug info and the other one without. Currently with this fix, the assembler will no longer
generate any debug info for the second .text section. And this is what GNU assembler
exactly did for this situation. So I think this still make some sense.