xbps-src: add make_check_pre

$make_check_pre can be used for wrapper commands like xvfb-run or
dbus-run-session which are common ways to make tests work. This way many
templates can avoid defining their own do_check function.

common/build-style/python3-module.sh

@@ -25,7 +25,7 @@ do_build() {
 
 do_check() {
 	if python3 -c 'import pytest' >/dev/null 2>&1; then
-		PYTHONPATH="$(cd build/lib* && pwd)" \
+		${make_check_pre} PYTHONPATH="$(cd build/lib* && pwd)" \
 			python3 -m pytest ${make_check_args} ${make_check_target}
 	else
 		# Fall back to deprecated setup.py test orchestration without pytest
@@ -37,7 +37,7 @@ do_check() {
 		fi
 
 		: ${make_check_target:=test}
-		python3 setup.py ${make_check_target} ${make_check_args}
+		${make_check_pre} python3 setup.py ${make_check_target} ${make_check_args}
 	fi
 }