[rmkit] set default CROSS_TC in docker_release.sh to arm-linux-gnueabihf for rm support

Author: okay

docker/Dockerfile.rm

@@ -5,3 +5,4 @@ RUN pip3 install okp
 WORKDIR /rmkit
 COPY . /rmkit/
 RUN rm src/build -fr
+ENV CROSS_TC=arm-linux-gnueabihf

scripts/build/docker_release.sh

@@ -1,7 +1,7 @@
 OUTDIR=artifacts
 TARGET=${TARGET:-rm}
 FBINK=${FBINK}
-CROSS_TC=${CROSS_TC}
+CROSS_TC=${CROSS_TC:-arm-linux-gnueabihf}
 
 mkdir ${OUTDIR}
 docker run -i --rm -v "${PWD}/${OUTDIR}:/mnt/artifacts" rmkit:${TARGET} /bin/bash << COMMANDS