clang - how to use alternate versions of gcc headers

I’m using clang native on intel-64bit system, Linux host
On this host there are different gcc installations e.g. gcc 4.5.0, gcc 4.6.2, gcc 4.7.0, as well as the system supplied default which is 4.4.6
When I build clang with default path, the system header files come from the system supplied gcc, Makes sense.
However, when I build clang in a shell where the path is gcc 4.7.0, I expected that the system headers would then come from the gcc 4.7 include directory,
But that is not the case, those files are still coming from the system supplied gcc. I checked the configure.log and indeed it is finding gcc 4.7.0
Any tips about how to point clang at different headers, either at compiler build time or (preferably) later? Or is this not possible? Thanks

I think there are two ways of doing it:

* Install clang on the same directory as gcc and it should work out of
the box (i have not tried it).
* Use the configure option --with-gcc-toolchain=path.

Cheers,
Rafael