do not hardcode the make

Index: Makefile.in
--- Makefile.in.orig
+++ Makefile.in
@@ -929,15 +929,15 @@ apidox:
 check: test
 
 test:
-	make -C src test
+	${MAKE_PROGRAM} -C src test
 
 leakcheck: leaktest
 
 leaktest:
-	make -C src leaktest
+	${MAKE_PROGRAM} -C src leaktest
 
 includetest:
-	make -C src includetest
+	${MAKE_PROGRAM} -C src includetest
 
 # Tell versions [3.59,3.63) of GNU make to not export all variables.
 # Otherwise a system limit (for SysV at least) may be exceeded.