Add support for compiling Windows ARM64EC

[MugundanMCW]

PR Description:

• ARM64EC (Emulation Compatible) is an application binary interface (ABI) for applications running on ARM-based Windows 11 devices. Code built for ARM64EC can interoperate with x64 code running under emulation, leveraging the native performance of ARM hardware.
• This PR adds support for building the AWS-C-Common library targeting Windows ARM64EC. The changes include conditional guards to exclude x64-specific code paths, enabling successful compilation for the ARM64EC architecture.