MAINT: Before make dist, only clean the build artefacts

The was breaking the CI release workflow because when `make build` is
run, coverage is not installed, yet the `clean-test` target used
`coverage erase`.

Author: has2k1

Makefile

@@ -103,7 +103,7 @@ release-minor:
 release-patch:
 	@$(PYTHON) ./tools/release-checklist.py patch
 
-dist: clean
+dist: clean-build
 	$(PYTHON) -m build
 	ls -l dist