Generalize EFI loader build scripts

[fbno]

Some improvements to the EFI loader build scripts:

• Allow compiling the code into a different directory out-of-source
• Support multiple versions of Visual Studio (2015-2019)
• Support up to edk2-stable201911 (newer versions are missing an Sha1Hmac API used in tpm12.c)
• Use nasm to compile the x64 assembly source (no manual build steps required anymore)
• Fix multiple dependency issues breaking the build
• Add short build documentation

[DavidXanatos]

cool thanks will check it out shortly

[AlxVD]

Anytime soon)?