gnuradio: gr-fec: add missing dependency to gsl

gr-fec needs gsl. Without this dependency cmake search gsl in the host system.
This issue produce errors like :

arm-buildroot-linux-uclibcgnueabihf-gcc: ERROR: unsafe header/library path used
in cross-compilation: '-I/usr/include'
make[3]: *** [gr-fec/lib/CMakeFiles/gnuradio-fec.dir/reed-solomon/encode_rs.c.o] Error 1

Signed-off-by: Gwenhael Goavec-Merou <gwenhael.goavec-merou@trabucayre.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>

package/gnuradio/Config.in

@@ -49,6 +49,7 @@ config BR2_PACKAGE_GNURADIO_CTRLPORT
 config BR2_PACKAGE_GNURADIO_FEC
 	bool "gr-fec support"
 	select BR2_PACKAGE_GNURADIO_BLOCKS
+	select BR2_PACKAGE_GSL
 	help
 	  FEC signal processing blocks
 

package/gnuradio/gnuradio.mk

@@ -89,6 +89,7 @@ GNURADIO_CONF_OPTS += -DENABLE_GR_DIGITAL=OFF
 endif
 
 ifeq ($(BR2_PACKAGE_GNURADIO_FEC),y)
+GNURADIO_DEPENDENCIES += gsl
 GNURADIO_CONF_OPTS += -DENABLE_GR_FEC=ON
 else
 GNURADIO_CONF_OPTS += -DENABLE_GR_FEC=OFF