"Universal" binaries in Linux?
 

I saw that with MacOS X it is possible to have what is called a "universal binary", which is basically a binary executable which supports multiple architectures. For example the sample output of a binary:

$ file libtest.dylib
libtest.dylib: Mach-O universal binary with 3 architectures
libtest.dylib (for architecture i386): Mach-O bundle i386
libtest.dylib (for architecture ppc): Mach-O bundle ppc
libtest.dylib (for architecture x86_64): Mach-O 64-bit bundle x86_64

Is this achievable under Linux? If it is, how would I go about doing this?

I've got one word for you.
Java.

Certainly universal, but it does not always have access to the native APIs. Even here a library that supports multiple architectures (Not OSs) could be useful.