libtorrent-rasterbar: fix cross for Python 3.8.

srcpkgs/libtorrent-rasterbar/template

@@ -1,7 +1,7 @@
 # Template file for 'libtorrent-rasterbar'
 pkgname=libtorrent-rasterbar
 version=1.2.2
-revision=2
+revision=3
 build_style=gnu-configure
 configure_args="--enable-examples --enable-python-binding
  --with-boost=${XBPS_CROSS_BASE}/usr
@@ -30,6 +30,20 @@ pre_configure() {
 	autoreconf -fi
 }
 
+pre_build() {
+	if [ "$CROSS_BUILD" ]; then
+		for f in ${XBPS_CROSS_BASE}/${py3_lib}/_sysconfigdata_*; do
+			f=${f##*/}
+			export _PYTHON_SYSCONFIGDATA_NAME=${f%.py}
+		done
+		export PYTHONPATH=${XBPS_CROSS_BASE}/${py3_lib}
+	fi
+}
+
+pre_install() {
+	pre_build
+}
+
 post_install() {
 	vlicense LICENSE
 }