test: Add makefile target for running unit tests

make check runs a bunch of other subtree tests that exercise code that
is hardly ever changed and have a comparatively long runtime. There
seems to be no target for running just the unit tests, so add one.

src/Makefile.test.include

@@ -419,7 +419,9 @@ bitcoin_test_check: $(TEST_BINARY) FORCE
 bitcoin_test_clean : FORCE
 	rm -f $(CLEAN_BITCOIN_TEST) $(test_test_bitcoin_OBJECTS) $(TEST_BINARY)
 
-check-local: $(BITCOIN_TESTS:.cpp=.cpp.test)
+check-unit: $(BITCOIN_TESTS:.cpp=.cpp.test)
+
+check-local: check-unit
 if BUILD_BITCOIN_TX
 	@echo "Running test/util/test_runner.py..."
 	$(PYTHON) $(top_builddir)/test/util/test_runner.py

src/test/README.md

@@ -15,7 +15,8 @@ that runs all of the unit tests. The main source file for the test library is fo
 Unit tests will be automatically compiled if dependencies were met in `./configure`
 and tests weren't explicitly disabled.
 
-After configuring, they can be run with `make check`.
+After configuring, they can be run with `make check`, which includes unit tests from
+subtrees, or `make && make -C src check-unit` for just the unit tests.
 
 To run the unit tests manually, launch `src/test/test_bitcoin`. To recompile
 after a test file was modified, run `make` and then run the test again. If you