toolchain/helpers.mk: use int as main() return type in checks

Although -Wmain-return-type is not considered as error (unlike
-Wimplicit-int), but just a warning, let's fix it for the future.

<stdin>:1:1: warning: return type of 'main' is not 'int' [-Wmain-return-type]

Signed-off-by: Petr Vorel <petr.vorel@gmail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
1 file changed