Our cc-wrapper is broken whenever the '-x' flag is used:
'gcc -x c foo.c -o bar' doesn't work the same way as 'gcc foo.c -o bar'
does. (Try both with NIX_DEBUG=1.)
What happens is that passing '-x' causes linker-related flags (such as
-Wl,-dynamic-linker) not to be added, just like if '-c' is passed.
The bug happens outside the multiple-outputs branch as well, but it
doesn't break imake there. It only breaks in multiple-outputs because
linking without -Wl,-dynamic-linker produces a binary with an invalid
ELF interpreter path. (Which arguably, is a bug in its own.)
