Creating a redistributable GCC package able to build dynamic libraries

Question

Case in point, a have a program that needs to be able to load dynamic libraries from runtime created arbitrary source files. The program is licensed under GPL. The program should ship as a package free of any external dependencies, ie. run out of an unzipped package.

Ideally, it should work as a portable, platform independent IDE (different binaries for different targets of course). Targets in mind are OSX 10.8++ and Windows, both in 32 and 64 bit formats. I need it to support C and C++ only.

I envision it as GCC placed in a subdirectory and invoked from a platform-supported script (like .bat files and bash etc.) with the goal of producing a dynamic library that can be loaded right away (ie. a DLL or a dylib) - through a classic commandline. The script will be fed with input / output files and include directories.

Can i use GCC for this - and how can i obtain/create such a package? Would this be legal from a license context? How about the standard library source files?

Any help with this project is hugely welcomed.