I'm not sure I understand why this makes ports harder. Shouldn't it be possible to port to a new system simply by porting Go 1.4 to that system? Once that base

I'm not sure I understand why this makes ports harder. Shouldn't it be possible to port to a new system simply by porting Go 1.4 to that system? Once that base version is ported, a script can build 1.4, then build 1.5 and any succeeding base versions until the current version is reached. Of course, system-specific features would have to be added for each go release beyond 1.4, but that would have to be done anyway. What am I missing?