REVIEW-4144:
- Move IncrementalCompilerBuilder to NativeBinaryServices
- Use CompileSpec instead task type to check whether import directives are supported or not.
In Long term this knowledge should live in the toolchain as it's toolchain specific
(GCC and Clang support #import for C and C++, but visual C++ does not)
REVIEW-4758 remove outputFile helper method (use objectFileFor instead)