Create "clean_residual_files" target in Makefile (elixir-lang#5982)

Additionally:

- Add /lib/*/_build/ to .gitignore, and delete folders

- Remove erl_crash.dump file in

- Mix fixtures
  - add lib/mix/test/fixtures/git_sparse_repo to the list of dirs to be removed
  - Sort and add a reminder in lib/mix/test/fixtures/.gitignore
    to update Makefile clean target when modifications are done

.gitignore

@@ -1,6 +1,7 @@
 /doc
 /ebin
-/lib/*/ebin/*
+/lib/*/ebin/
+/lib/*/_build/
 /lib/*/tmp
 /lib/elixir/src/*_parser.erl
 /lib/elixir/src/elixir.app.src

Makefile

@@ -16,7 +16,7 @@ INSTALL_PROGRAM = $(INSTALL) -m755
 GIT_REVISION = $(strip $(shell git rev-parse HEAD 2> /dev/null ))
 GIT_TAG = $(strip $(shell head="$(call GIT_REVISION)"; git tag --points-at $$head 2> /dev/null | tail -1) )
 
-.PHONY: install compile erlang elixir build_plt clean_plt dialyze test clean install_man clean_man docs Docs.zip Precompiled.zip zips
+.PHONY: install compile erlang elixir build_plt clean_plt dialyze test clean clean_residual_files install_man clean_man docs Docs.zip Precompiled.zip zips
 .NOTPARALLEL: compile
 
 #==> Functions
@@ -116,17 +116,25 @@ clean:
 	cd lib/elixir && $(REBAR) clean
 	rm -rf ebin
 	rm -rf lib/*/ebin
-	rm -rf lib/elixir/test/ebin
-	rm -rf lib/*/tmp
-	rm -rf lib/mix/test/fixtures/git_repo
-	rm -rf lib/mix/test/fixtures/deps_on_git_repo
-	rm -rf lib/mix/test/fixtures/git_rebar
 	rm -rf lib/elixir/src/elixir.app.src
-	$(MAKE) clean_man
+	rm -f Docs-v*.zip
+	rm -f Precompiled-v*.zip
+	$(Q) $(MAKE) clean_residual_files
 
 clean_exbeam:
 	$(Q) rm -f lib/*/ebin/Elixir.*.beam
 
+clean_residual_files:
+	rm -rf lib/*/_build/
+	rm -rf lib/*/tmp/
+	rm -rf lib/elixir/test/ebin/
+	rm -rf lib/mix/test/fixtures/deps_on_git_repo/
+	rm -rf lib/mix/test/fixtures/git_rebar/
+	rm -rf lib/mix/test/fixtures/git_repo/
+	rm -rf lib/mix/test/fixtures/git_sparse_repo/
+	rm -f erl_crash.dump
+	$(Q) $(MAKE) clean_man
+
 #==> Documentation tasks
 
 LOGO_PATH = $(shell test -f ../docs/logo.png && echo "--logo ../docs/logo.png")
@@ -170,7 +178,7 @@ docs_logger: compile ../ex_doc/bin/ex_doc
 	@ echo "ex_doc is not found in ../ex_doc as expected. See README for more information."
 	@ false
 
-#==> Zips
+#==> Zips tasks
 
 Docs.zip: docs
 	rm -rf Docs-v$(VERSION).zip

lib/mix/test/fixtures/.gitignore

@@ -1,4 +1,6 @@
-git_repo
-git_sparse_repo
-deps_on_git_repo
-git_rebar
+# Remember to update Makefile "clean_residual_files" target for any modifications
+# made in this file
+/deps_on_git_repo/
+/git_rebar/
+/git_repo/
+/git_sparse_repo/