net-snmp: InstallDev fix

Commit 384c2a8cfd added support for symlinking
net-snmp-config into $(STAGING_DIR)/usr/bin but forgot to install first
$(STAGING_DIR)/usr/bin resulting into a compile issue if
$(STAGING_DIR)/usr/bin is not yet present.

Signed-off-by: Hans Dedecker <dedeckeh@gmail.com>

net/net-snmp/Makefile

@@ -228,6 +228,7 @@ define Build/InstallDev
 	$(INSTALL_DIR) $(2)/bin
 	$(INSTALL_BIN) $(PKG_INSTALL_DIR)/usr/bin/net-snmp-config $(2)/bin/
 	$(SED) 's,=/usr,=$(STAGING_DIR)/usr,g' $(2)/bin/net-snmp-config
+	$(INSTALL_DIR) $(STAGING_DIR)/usr/bin
 	$(LN) $(STAGING_DIR)/host/bin/net-snmp-config $(STAGING_DIR)/usr/bin/
 
 	$(INSTALL_DIR) $(1)/usr/include