gcc 4.9.x: Exclude for PPC SPE because of PR60102

Exclude gcc 4.9.x for PowerPC SPE toolchains because of an ICE
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=60102


There's a patch available but it's somewhat intrusive with PPC in
general and hasn't been well tested yet.

Signed-off-by: Gustavo Zacarias <gustavo@zacarias.com.ar>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>