feat: xz-compress duckdb sources in the tarball

.Rbuildignore

@@ -43,3 +43,4 @@ _files$
 ^compile_commands\.json$
 ^\.cache$
 ^tests/testthat/helper-rethrow\.R$
+^cleanup$

cleanup

@@ -0,0 +1,7 @@
+#!/bin/sh
+
+set -ex
+
+cd src
+tar cvJf duckdb.tar.xz duckdb
+rm -rf duckdb

configure

@@ -27,3 +27,10 @@ if [ -f "${DUCKDB_R_PREBUILT_ARCHIVE}" ] && tar -xm -f ${DUCKDB_R_PREBUILT_ARCHI
 else
   cp include/to-tar.mk Makevars.duckdb
 fi
+
+# The duckdb sources are xz-compressed in the tarball to keep it under 5000000 bytes.
+# This happens in the cleanup script.
+
+if [ -f duckdb.tar.xz ]; then
+  tar xf duckdb.tar.xz
+fi

configure.win

@@ -33,3 +33,10 @@ if [ -f "${DUCKDB_R_PREBUILT_ARCHIVE}" ] && tar -xm --force-local -f ${DUCKDB_R_
 else
   cp include/to-tar-win.mk Makevars.duckdb
 fi
+
+# The duckdb sources are xz-compressed in the tarball to keep it under 5000000 bytes.
+# This happens in the cleanup script.
+
+if [ -f duckdb.tar.xz ]; then
+  tar xf duckdb.tar.xz
+fi