Make x86 target flags more specific

[tobil4sk]

As discussed in #1813, -64 and -32 are currently used in a lot of places to mean x86_64 and x86_32 respectively. Now that arm64 systems are widespread (and 8.2.0-Dev has arm64 Mac support), which is also a 64 bit architecture, it would be better to have more specific flags that are specifically for x86 architectures.

It looks like the ios target already uses the i386 flag:

lime/src/lime/tools/IOSHelper.hx

Line 124 in ca52db8

if (project.targetFlags.exists("i386") || project.targetFlags.exists("32"))

[joshtynjala]

Interesting background here on x86, i386, and IA-32, which all can refer to 32-bit Intel architecture processors: https://unix.stackexchange.com/questions/489145/why-do-linux-world-use-the-term-i386-instead-of-x86

Similarly, 64-bit Intel/AMD can be x86_64, x64, AMD64, and Intel 64 (but not IA-64, which was used for Intel Itanium instead).