Use https for downloading libpcap

build/Dockerfile

@@ -74,7 +74,7 @@ RUN chmod -R a+w /usr/local/go
 # The libpcap version from Debian packages is 1.6.2, matching that version here although newer versions of libpcap have been released
 # We have to cross-compile the libpcap library for the new architectures, that's what we're doing here
 ENV LIBPCAP_CROSS_VERSION=1.6.2
-RUN curl -sSL http://www.tcpdump.org/release/libpcap-${LIBPCAP_CROSS_VERSION}.tar.gz | tar -xz \
+RUN curl -sSL https://www.tcpdump.org/release/libpcap-${LIBPCAP_CROSS_VERSION}.tar.gz | tar -xz \
 	&& cd libpcap-${LIBPCAP_CROSS_VERSION} \
 	&& for crosscompiler in ${GCC_CROSSCOMPILERS}; do \
 		CC=${crosscompiler}-gcc ac_cv_linux_vers=2 ./configure --host=${crosscompiler} --with-pcap=linux \