Individual toolchain installation should be ignored for full_sdk

[asemjonovs]

trafficstars

Running setup.sh -t all with a Full SDK downloads and installs all the toolchains again. This should be ignored or provide a warning when using the Full SDK.

[yperess]

For more information on this, we have a build environment that doesn't have wget. We would also need the check_command wget 91 line moved to just before it's actually used. I think that if we move it into the loop for toolchain in ${inst_toolchains[@]}; do then it would work.