don't tar old nonexistent files, call "find" correctly

Makefile

@@ -173,7 +173,7 @@ distclean: build-clean
 bootstrap-clean:
 	rm -rf config/install-sh config/compile config/config.guess config/config.sub config/missing configure build/make/Makefile-auto.in
 	rm -f src/doc/en/installation/*.txt
-	find src/doc/en/reference/spkg -name index.rst -prune -o -maxdepth 1 -name "*.rst" -exec rm -f {} \+
+	find src/doc/en/reference/spkg -maxdepth 1 -name index.rst -prune -o -name "*.rst" -exec rm -f {} \+
 	for a in environment environment-optional src/environment src/environment-optional; do rm -f $$a.yml $$a-3.[89].yml $$a-3.1[0-9].yml; done
 	rm -f src/requirements.txt
 	rm -f src/setup.cfg

bootstrap

@@ -224,8 +224,8 @@ save () {
 	config/install-sh config/compile config/config.guess config/config.sub config/missing \
 	build/make/Makefile-auto.in \
 	src/doc/en/installation/*.txt \
-	$(find src/doc/en/reference/spkg -name index.rst -prune -o -maxdepth 1 -name "*.rst" -print) \
-	environment-3.[89]-*.yml environment-3.1[0-9]-*.yml \
+	$(find src/doc/en/reference/spkg -maxdepth 1 -name index.rst -prune -o -name "*.rst" -print) \
+	environment-3.1[0-9]-*.yml \
 	src/pyproject.toml \
 	src/requirements.txt \
 	src/setup.cfg \