Build with libcurl for new keylocation=https://

following commit da40a1b007d2a99bac95bd67ec6dd7b8e217c0cf from
debian-upstream.

However since some of our rust-packages seem to depend on
libcurl4-gnutls-dev (via librust-curl-sys-dev) we add a
option for the dependency - I would assume that both should work
equally well (the callers are in upstream/lib/libzfs/libzfs_crypto.c)

Signed-off-by: Stoiko Ivanov <s.ivanov@proxmox.com>

debian/control

@@ -6,6 +6,7 @@ Build-Depends: abigail-tools,
                debhelper-compat (= 12),
                dh-python,
                libblkid-dev,
+               libcurl4-openssl-dev | libcurl4-gnutls-dev,
                libelf-dev,
                libpam0g-dev,
                libssl-dev | libssl1.0-dev,
@@ -84,9 +85,12 @@ Package: libzfs4linux
 Section: contrib/libs
 Architecture: linux-any
 Depends: ${misc:Depends}, ${shlibs:Depends}
+# The libcurl4 is loaded through dlopen("libcurl.so.4").
+# https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=988521
+Recommends: libcurl4
 Breaks: libzfs2, libzfs2linux, libzfs3linux, libzfs4
 Replaces: libzfs2, libzfs2linux, libzfs3linux, libzfs4
-Description: OpenZFS filesystem library for Linux
+Description: OpenZFS filesystem library for Linux - general support
  OpenZFS is a storage platform that encompasses the functionality of
  traditional filesystems and volume managers. It supports data checksums,
  compression, encryption, snapshots, and more.