In r135308, -save-temps was modified to prevent a temporary file from

overwriting the input file.  For example,

clang -c foo.s -o foo.o -save-temps

Unfortunately, the original patch didn't compare the paths of the input and
output files.  Thus, something like the following would fail to create foo.s.

cd /tmp/obj
clang -c ../src/foo.s -o foo.o -save-temps

rdar://11252615

llvm-svn: 155224