package/clamav: fix build on mips64el

Fixes:
http://autobuild.buildroot.net/results/b64/b640937f35b11ddb9f1e29f0e44040eda8850f26/
'Could not find specification for target "mips64el-unknown-linux-gnu".'

This patch changes
    -DRUST_COMPILER_TARGET=mips64el-unknown-linux-gnu
to
    -DRUST_COMPILER_TARGET=mips64el-unknown-linux-gnuabi64

Signed-off-by: Bernd Kuhls <bernd.kuhls@t-online.de>
Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>

package/clamav/clamav.mk

@@ -54,7 +54,7 @@ CLAMAV_CONF_OPTS = \
 	-DENABLE_MILTER=OFF \
 	-DENABLE_TESTS=OFF \
 	-DHAVE_SYSTEM_LFS_FTS=ON \
-	-DRUST_COMPILER_TARGET=$(ARCH)-unknown-$(TARGET_OS)-$(LIBC)$(ABI) \
+	-DRUST_COMPILER_TARGET=$(RUSTC_TARGET_NAME) \
 	-Dtest_run_result=ON \
 	-Dtest_run_result__TRYRUN_OUTPUT=ON