When using the IAR Compiler without a license, CMake issues a
fatal error message about a missing linker and librarian.
This message is misleading.

In the previous detection, CMakeFindBinUtils.cmake would rely
on information collected from try_compile() which depends on a
working license.

In the new detection scheme, the IAR BinUtils are automatically
detected regardless of an existing license, based solely on the
compiler's path.

The failure point will be when trying to compile a C or a CXX
source file, where there will be no CMAKE_${lang}_COMPILER_VERSION
available.

This change improves the resulting message for when trying to use
the compiler without a license.