do not try to package libstdc++.so in static mode

package/libstdcxx/Makefile

@@ -19,7 +19,7 @@ BUILD_STYLE:=		manual
 INSTALL_STYLE:=		manual
 
 do-install:
-ifeq ($(ADK_TARGET_BINFMT_FLAT),)
+ifeq ($(ADK_TARGET_BINFMT_FLAT)$(ADK_TARGET_USE_STATIC_LIBS_ONLY),)
 	${INSTALL_DIR} ${IDIR_LIBSTDCXX}/usr/${ADK_TARGET_LIBC_PATH}
 ifeq ($(ADK_TARGET_ARCH_SH),y)
 ifeq ($(ADK_TARGET_CPU_SH_SH3),y)