external: Remove -m64 from shared CFLAGS on ARM
external: Remove -m64 from shared CFLAGS on ARM

-m64 isn't an ARM flag.

Signed-off-by: Brad Bishop <713d098c0be4c8fd2bf36a94cd08699466677ecd@fuzziesquirrel.com>
Signed-off-by: Stewart Smith <ec31ab75ddf977353c8f660f92ea8b23f64aef25@linux.vnet.ibm.com>

mikey/skiboot,qemu/skiboot,shenki/skiboot,open-power/skiboot,open-power/skiboot,legoater/skiboot,qemu/skiboot,open-power/skiboot,shenki/skiboot,stewart-ibm/skiboot,stewart-ibm/skiboot,legoater/skiboot,qemu/skiboot,mikey/skiboot,stewart-ibm/skiboot,qemu/skiboot,qemu/skiboot,legoater/skiboot,legoater/skiboot,mikey/skiboot,legoater/skiboot,open-power/skiboot,shenki/skiboot,shenki/skiboot,shenki/skiboot,open-power/skiboot