mkdir build
cd build
>>../src/for-test.sd.mk
+>>../lib/for-test.mk.in
.././autogen.sh && ../configure
make -j4 all check
make -j4
grep '^# for-check 1' src/Subdir.mk || false
+echo '# for-check 2' >>../lib/for-test.mk.in
+make -j4
+grep '^# for-check 2' lib/for-test.mk || false
+
echo ok.