We don't want a dynamic dependency in the library that we ship, so link it
statically by configuring curl-sys's build script to not pick up the system
version via pkg-config.
--enable-extended \
--enable-sanitizers
ENV SCRIPT python2.7 ../x.py dist --host $HOSTS --target $HOSTS
+
+# This is the only builder which will create source tarballs
ENV DIST_SRC 1
+
+# When we build cargo in this container, we don't want it to use the system
+# libcurl, instead it should compile its own.
+ENV LIBCURL_NO_PKG_CONFIG 1