buildroot

toolchain: allow for stupid toolchains

check_arm_abi builds a test C file to check that the toolchain is
working correctly, with the output redirected to /dev/null.

However, some toolchains (OSELAS 2014.12.0, for instance) foolishly
append ".gdb" to the output filename for an intermediate file, causing
an attempt to write to /dev/null.gdb, which obviously fails.

Fix this by adding changing the output to a temporary file, which is
later removed along with any other "suffixed" files.

Suggested-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Signed-off-by: Guido Martínez <guido@vanguardiasur.com.ar>
Reviewed-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>