package/libraw: depends on BR2_TOOLCHAIN_HAS_SYNC_4

package/libraw: depends on BR2_TOOLCHAIN_HAS_SYNC_4

libraw needs __sync_fetch_and_add since version 0.20.0 and
https://github.com/LibRaw/LibRaw/commit/d1975cb0e055d2bfe58c9d845c9a3e57c346a2f9

This will fix the following build failure with imagemagick which is
raised since commit 2f47cfade4b298350d056f6d9a7525b837e2ba23:

/home/buildroot/autobuild/run/instance-0/output-1/host/opt/ext-toolchain/bin/../lib/gcc/sparc-buildroot-linux-uclibc/9.3.0/../../../../sparc-buildroot-linux-uclibc/bin/ld: /home/buildroot/autobuild/run/instance-0/output-1/host/sparc-buildroot-linux-uclibc/sysroot/usr/lib/libraw_r.so: undefined reference to `__sync_fetch_and_add_4'

Fixes:
 - http://autobuild.buildroot.org/results/900df43bd418d2da0c3ec875db1c5564dd857e94

Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>