Darwin/iOS: Improve unified syntax use for LLVM
Darwin: Modernize build scripts, include arm64
Darwin: Rebuild Xcode project, include 64bit parts
Darwin/x86_64: Fix 64-bit type shortening warnings
Darwin/aarch64: Fix invalid reference in assembly
Darwin/aarch64: Use CNAME, restrict .size like ARM
Darwin/aarch64: Account for long double being equal to double
Darwin/aarch64: Use Clang cache invalidation builtin
Darwin/aarch64: Fix "shadows declaration" warnings
Darwin/aarch64: Fix size_t assumptions
Darwin/aarch64: Respect iOS ABI re: stack argument alignment