Docs: Use native windows CMake version for Cygwin

Native version of CMake must be used on windows for Cygwin, Cygwin
specific version will not work. Add more detailed explanation of
build software requirement in the use guide documents.

Change-Id: Ib3daacb7f24c8b011ac9f877aa5db5ab2be8c0a1
Signed-off-by: Mingyang Sun <mingyang.sun@arm.com>