Refactor EDK2 build script for improved clarity and efficiency

[tsvenbla]

Refactor EDK2 build script for improved clarity and efficiency

• Implement a case statement for setting architecture and postfix based on the input argument, enhancing readability and scalability.
• Add a directory change check to exit the script if the cd command to the EDK2 source directory fails, improving robustness.
• Consolidate file removal commands into a single line for each set of related files, simplifying the script structure.
• Streamline the build commands with a conditional segment specifically for the AARCH64 architecture, making the script more concise.
• Enhance the success check logic by verifying the existence of all expected output files before declaring success.

Note that I did not test this change, so merge after testing only.