When compiling in an alternate SYSROOT things generally work great as long as your SYSROOT is the same as the one the toolchain was configured with when it was compiled, usually /usr/$CHOST. GCC and friends provide a --sysroot command line argument for changing this at run-time but don't use the $SYSROOT environment variable so unless every package build system you encounter is cooperative changing SYSROOT is prone to errors. Thats where these tools come in. All they do is provide wrappers for GCC and other utilities that add --sysroot to the command line arguments if $SYSROOT is defined. The code is based in part on ccache since it uses the same sort of GCC wrapping scheme.
TODO
Portions of this code came from ccache 3.1.9 and which is licensed under the GNU GPL version 3 or later. The full license text can be found in GPL-3.0.txt and at http://www.gnu.org/licenses/gpl-3.0.html. The copyright for ccache is as follows:
Copyright (C) 2002-2007 Andrew Tridgell
Copyright (C) 2009-2011 Joel Rosdahl
The copyright for sysroot-wrappers as a whole is as follows:
Copyright (C) 2013 The CoreOS Authors.