gnu: rsync: Enable zstd & lz4 compression.

Both are ridiculously more suited to this role than the old zlib
compressor.  The closure size increase is negligible (1 MiB or 1.3% for
zstd, 1.7 MiB for both).

* gnu/packages/rsync.scm (rsync-next)[inputs]: Add zstd:lib and lz4.
[arguments]: Remove the corresponding "--disable-zstd" and
"--disable-lz4" #:configure-flags.

gnu/packages/rsync.scm

@@ -87,16 +87,16 @@ files in the destination.")
       (list "--without-included-zlib"
             "--without-included-popt"
             ;; Avoid these dependencies for now.
-            "--disable-lz4"
-            "--disable-openssl"
-            "--disable-zstd")))
+            "--disable-openssl")))
    (native-inputs
     `(("perl" ,perl)))
    (inputs
     `(("acl" ,acl)
+      ("lz4" ,lz4)
       ("popt" ,popt)
       ("xxhash" ,xxhash)
-      ("zlib" ,zlib)))
+      ("zlib" ,zlib)
+      ("zstd:lib" ,zstd "lib")))
    (synopsis "Remote (and local) file copying tool")
    (description
     "Rsync is a fast and versatile file copying tool.  It can copy locally,