Well I would like to, but there doesn't seem to be Clang 3 or GCC 4 on any of the classic Amiga or on OS4/MorphOS. I don't have any interest in using a non standard compiler
You asking this question in the wrong forum, this forum is mostly where classic Amiga users are.
I will try to answer you questions anyway.
Clang = No.
GCC Version is 4.2.4.
GIT = Almost.
http://jamiga2.blogspot.no/we have some thing that almost does it.
http://os4depot.net/index.php?function=showfile&file=development/utility/hggit.lhaUnless your thinking about using a cross compiler, you can forget about GIT, and use SVN instead.
also need to research how POSIX compliant AmigaOS is as all of the C I code has to be POSIX compliance (I am a huge fan of System V) and all of my associates mostly code POSIX applications and use git, so we'll see how feasible it will be.
Its not fully POSIX complainant, you can compile some Linux shell stuff whit out any changes, but most thing if its a bit more complicated, will need AmigaOS platform dependent code.
Some build tools are not available, some configure scripts and depends on Linux to work so want work on AmigaOS, in some cases you most cross compile or generate the makefiles on Linux or Cygwin first.
Gui toolkits we have support for QT, no other cross platform GUI toolkit is supported. So if you have GUI based program in most cases you need to make a different GUI for the AmigaOS version.
Cross platform Graphics toolkits: SDL and Allegro.
