systemd: Explicitly add hidden attribute to __start_BUS_ERROR_MAP and __stop_BUS_ERROR_MAP
These symbols appear in dynsyms of libsystemd.so and musl loader
doesnt like it
Error relocating /mnt/a/oe/build/tmp/work/i586-bec-linux-musl/avahi/0.7-r0/recipe-sysroot//lib/libsystemd.so.0: __start_BUS_ERROR_MAP: symbol not found
Error relocating /mnt/a/oe/build/tmp/work/i586-bec-linux-musl/avahi/0.7-r0/recipe-sysroot//lib/libsystemd.so.0: __stop_BUS_ERROR_MAP: symbol not found
[YOCTO #12577]
Signed-off-by: Khem Raj <raj.khem@gmail.com> Signed-off-by: Ross Burton <ross.burton@intel.com>
