As for the C compiler, it is now available via opkg.
opkg update
opkg install binutils
opkg install make
opkg install tar
opkg install yun-gccI installed it on my yun expanded on an SD.
I was very impressed by it's performance.
I had to learn much more than expected about *@#$%! openwrt package/makefiles than I expected to get that put together and still can't put one together easily.
I am very pleased with the functionality of yun-gcc at this point. It seems to be able to compile anything the hardware supports if you are willing to find and fill all the dependencies.