[Embedded] Add ARMv5TE to list of recognized architectures

[colemancda]

Adds support for Swift Embedded ARMv5TE target (e.g. Nintendo DS). This adds ARMv5TE as a recognized embedded architecture and builds a stdlib module for it.
Since LLVM natively supports ARMv5TE, this is all that's needed to write Swift for the Nintendo DS. Right now this is needed for swift-embedded-nds, which is currently just compiling for Armv4 since its backwards compatible.

[harlanhaskins]

Part of me also wonders what the more substainable version of this is; I added armv4t exclusively for Game Boy Advance, and I think it's fine to add armv5te for NDS, but I feel like there's gotta be a better answer for esoteric architecture stdlibs without forcing the main toolchain to embed the additional modules. Maybe like a swift-toolchain-extras repo that contains more supported architectures you need to opt into via Package.swift.