tcpdump: fix pcap-config issues

The patch removes a libpcap check to avoid a problem with libpcap. Fix
libpcap instead.

Modernize Makefile:

Use a normal autoconf bool instead of checking for CONFIG_IPV6.

Remove old configure and MAKE_FLAGS hacks. Removing them results in
compilation continuing to work without a problem.

Signed-off-by: Rosen Penev <rosenp@gmail.com>

package/network/utils/tcpdump/Makefile

@@ -9,20 +9,19 @@ include $(TOPDIR)/rules.mk
 
 PKG_NAME:=tcpdump
 PKG_VERSION:=4.9.3
-PKG_RELEASE:=2
+PKG_RELEASE:=3
 
 PKG_SOURCE:=$(PKG_NAME)-$(PKG_VERSION).tar.gz
 PKG_SOURCE_URL:=http://www.us.tcpdump.org/release/ \
 	http://www.tcpdump.org/release/
 PKG_HASH:=2cd47cb3d460b6ff75f4a9940f594317ad456cfbf2bd2c8e5151e16559db6410
 
-PKG_BUILD_PARALLEL:=1
-
 PKG_MAINTAINER:=Felix Fietkau <nbd@nbd.name>
 PKG_LICENSE:=BSD-3-Clause
 PKG_CPE_ID:=cpe:/a:tcpdump:tcpdump
 
 PKG_INSTALL:=1
+PKG_BUILD_PARALLEL:=1
 
 include $(INCLUDE_DIR)/package.mk
 
@@ -47,36 +46,18 @@ endef
 
 CONFIGURE_ARGS += \
 	--without-cap-ng \
-	--without-crypto
-
-ifeq ($(CONFIG_IPV6),y)
-CONFIGURE_ARGS += \
-	--enable-ipv6
-endif
+	--without-crypto \
+	$(call autoconf_bool,CONFIG_IPV6,ipv6)
 
 TARGET_CFLAGS += -ffunction-sections -fdata-sections
 TARGET_LDFLAGS += -Wl,--gc-sections
 
-CONFIGURE_VARS += \
-	BUILD_CC="$(TARGET_CC)" \
-	HOSTCC="$(HOSTCC)" \
-	td_cv_buggygetaddrinfo="no" \
-	ac_cv_linux_vers=$(LINUX_VERSION) \
-	ac_cv_header_rpc_rpcent_h=no \
-	ac_cv_lib_rpc_main=no \
-	ac_cv_path_PCAP_CONFIG=""
-
-MAKE_FLAGS :=
-
 ifeq ($(BUILD_VARIANT),mini)
   TARGET_CFLAGS += -DTCPDUMP_MINI
   CONFIGURE_ARGS += --disable-smb
   MAKE_FLAGS += TCPDUMP_MINI=1
 endif
 
-MAKE_FLAGS += \
-	CCOPT="$(TARGET_CFLAGS)" INCLS="-I. $(TARGET_CPPFLAGS)"
-
 define Package/tcpdump/install
 	$(INSTALL_DIR) $(1)/usr/sbin
 	$(INSTALL_BIN) $(PKG_INSTALL_DIR)/usr/sbin/tcpdump $(1)/usr/sbin/