[HIPIFY] hipify-clang's include semantics change based on the existence of -o

[ChrisKitching]

STR:

1. Create an empty file called test.h
2. Create a file called test.cpp containing only #include "test.h"
3. Run: hipify-clang test.cpp -- -x cuda --cuda-path=<whatever> - works correctly
4. Run: hipify-clang -o test.hip test.cpp -- -x cuda --cuda-path=<whatever> - works correctly
5. Run: hipify-clang -o /any/other/directory/test.hip test.cpp -- -x cuda --cuda-path=<whatever> - Fails:

/home/chris/spectral/xcmake/src/../wat.hip.hip:1:10: fatal error: 'test.h' file not found
#include "test.h"
         ^~~~~~~~
1 error generated.
Error while processing /home/chris/spectral/xcmake/src/../wat.hip.hip.

It seems that the output path is being used to resolve includes, and hence relative includes fail if you set an output path in a different directory.

[ChrisKitching]

ROCm/HIP#210 Should also resolve this. Not sure why github's auto-citation thingy didn't pickup on that.