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

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

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@155224 91177308-0d34-0410-b5e6-96231b3b80d8