Add compilation support for the TileGX architecture

This patch adds compilation support for the TileGx architecture. Since
the tests were not ran on other architectures of the Tile family
(Tile64, TIlepro), errors are triggered during compilation if the
architecture is another Tile arch.

Signed-off-by: Simon Marchi <simon.marchi@polymtl.ca>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>