transmission: fix uTP enabled build with ccache

Transmission would incorrectly determine the C++ compiler when ccache is
enabled, causing a build with uTP to fail at the configure step.
This patch adds a patch against transmission, fixing the problem.

Signed-off-by: Thomas De Schampheleire <thomas.de.schampheleire@gmail.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>