iperf3: enable native builds

Enable native variants of iperf3 tool for SDK builds.

Signed-off-by: Denis Mukhin <dmukhin@ford.com>
Signed-off-by: Khem Raj <raj.khem@gmail.com>

meta-oe/recipes-benchmark/iperf3/iperf3_3.18.bb

@@ -30,3 +30,5 @@ PACKAGECONFIG[lksctp] = "ac_cv_header_netinet_sctp_h=yes,ac_cv_header_netinet_sc
 PACKAGECONFIG[openssl] = "--with-openssl=${RECIPE_SYSROOT}${prefix},--without-openssl,openssl"
 
 CFLAGS += "-D_GNU_SOURCE"
+
+BBCLASSEXTEND = "native nativesdk"