patch 8.2.0290: running individual test differs from all tests

Problem:    Running individual test differs from all tests.
Solution:   Pass on environment variables. (Yee Cheng Chin, closes #5672)
diff --git a/src/testdir/Makefile b/src/testdir/Makefile
index a0520e0..746c849 100644
--- a/src/testdir/Makefile
+++ b/src/testdir/Makefile
@@ -73,7 +73,7 @@
 # 	make test_largefile
 $(NEW_TESTS):
 	rm -f $@.res test.log messages
-	@MAKEFLAGS=--no-print-directory $(MAKE) -f Makefile $@.res
+	@MAKEFLAGS=--no-print-directory $(MAKE) -f Makefile $@.res VIMPROG=$(VIMPROG) XXDPROG=$(XXDPROG) SCRIPTSOURCE=$(SCRIPTSOURCE)
 	@cat messages
 	@if test -f test.log; then \
 		exit 1; \