Comment 8 for bug 240884

Actually, I should have recognized the problem just from the description.
Asking the assembler to generate dwarf debug info, when the file already has
debug info generated by the compiler, is just one of those things you should not
do. Of course, the assembler ought to give a better error message..

You see, the compiler emits file and line number info referring to the C (or
other language) source file and line numbers, while "as -g" emits file and line
number info for the assembly file. Having both sets of debug info doesn't make
much sense, since they give contradictory information.