Sources for this prebuilt toolchain can be downloaded from Linaro
at http://android-build.linaro.org/

For the exact versions, look at the toolchain build matching the
release used here, e.g. if you're interested in the sources for
the 2013.05 prebuilts, use
http://android-build.linaro.org/~linaro-android/toolchain-4.8-2013.05