…sts and that the SDK header files are found. At least, it checks if the SDK include_h folder exists and assumes the headers are in there. -nostdinc, -nostartfiles and -nostdlib are now moved to the OPTIONS variable which is propagated throughout the necessary fules

The makefile will perform a check to ensure that a cross compiler exi…

…ct use -nostdinc parameter

…nce of the already existing cross compiler and the SDK include path should only happen when it is necessary. The checking has been moved into the 'prepare' rule since that is prequisite for actually building clib4. Before this commit, it would mean that you would have to provide a valid cross-compiler to be available on the PATH even if you just wanted to make 'clean'.

…ariable is the actual compiler. Mostly, this will be the case, but with ADTOOLS CC is assigned to something of the pattern: ppc-amigaos-gcc -B /some/Location. This will cause which to fail

Added some targets that are PHONY targets. The checking of the existe…