Fetch the test tar ball to a subdirectory in ${S}. This avoids the
following error after having done `devtool modify libxml2`:
| DEBUG: Executing shell function do_configure
| find: ‘.../build/tmp/work/mips32r2el-nf-poky-linux/libxml2/2.9.4-r0/xmlconf/’: No such file or directory
Signed-off-by: Peter Kjellerstedt <peter.kjellerstedt@axis.com> Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
