Clang-cl will fail to build and produce warnings about redefining existing symbols, mostly for float.h and math.h compatibility.
To resolve this, this moves the clang-cl detection earlier in the CMakeLists.txt so that CLANG_CL can be checked properly where there is an existing MSVC workaround for these symbols.
This resolves the build using the latest clang-cl from the LLVM clang repo as well as clang-cl that can be installed with MSVC 2022.
Signed-off-by: Tyler Erickson <tyler.erickson@seagate.com>
