perl: simplify passing in ldflags

Originally as PR #2383 but rewritten.

Signed-off-by: Philip Prindeville <philipp@redfish-solutions.com>
Signed-off-by: Alexander Ryzhov <openwrt@ryzhov-al.ru>

lang/perl/files/base.config

@@ -1008,7 +1008,7 @@ ccflags="-D_LARGEFILE_SOURCE -D_FILE_OFFSET_BITS=64 $owrt:cflags"
 ccflags_uselargefiles='-D_LARGEFILE_SOURCE -D_FILE_OFFSET_BITS=64'
 ccdlflags="-fPIC -Wl,-rpath,$owrt:perllibpath/CORE"
 cccdlflags='-fPIC'
-ldflags=''
+ldflags="$owrt:ldflags"
 ldflags_uselargefiles=''
 lddlflags="-shared $owrt:ldflags"