buildsystem: various small improvements (#6598)

Follow-up of #6101.

- Makefile:

Set all as actual default target.

- contrib/devtools/Makefile:

The buf target was running unconditionally.

Install protoc-gen-gocosmos along with protoc.

contrib/devtools/Makefile

@@ -60,7 +60,7 @@ tools-stamp: proto-tools statik runsim
 # Install the runsim binary with a temporary workaround of entering an outside
 # directory as the "go get" command ignores the -mod option and will polute the
 # go.{mod, sum} files.
-# 
+#
 # ref: https://github.com/golang/go/issues/30515
 statik: $(STATIK)
 $(STATIK):
@@ -70,7 +70,7 @@ $(STATIK):
 # Install the runsim binary with a temporary workaround of entering an outside
 # directory as the "go get" command ignores the -mod option and will polute the
 # go.{mod, sum} files.
-# 
+#
 # ref: https://github.com/golang/go/issues/30515
 runsim: $(RUNSIM)
 $(RUNSIM):
@@ -85,7 +85,7 @@ ifeq ($(UNAME_S),Darwin)
   PROTOC_ZIP ?= protoc-3.11.2-osx-x86_64.zip
 endif
 
-proto-tools: proto-tools-stamp protoc-gen-gocosmos buf
+proto-tools: proto-tools-stamp buf
 
 proto-tools-stamp:
 	@echo "Installing protoc compiler..."
@@ -95,7 +95,14 @@ proto-tools-stamp:
 	unzip -o ${PROTOC_ZIP} -d $(PREFIX) 'include/*'; \
 	rm -f ${PROTOC_ZIP})
 
-buf: 
+	@echo "Installing protoc-gen-gocosmos..."
+	@go install github.com/regen-network/cosmos-proto/protoc-gen-gocosmos
+
+	touch $@
+
+buf: buf-stamp
+
+buf-stamp:
 	@echo "Installing buf..."
 	@curl -sSL \
     "https://github.com/bufbuild/buf/releases/download/v${BUF_VERSION}/buf-${UNAME_S}-${UNAME_M}" \
@@ -104,13 +111,8 @@ buf:
 
 	touch $@
 
-protoc-gen-gocosmos:
-	@echo "Installing protoc-gen-gocosmos..."
-	@go install github.com/regen-network/cosmos-proto/protoc-gen-gocosmos
-
 tools-clean:
 	rm -f $(STATIK) $(GOLANGCI_LINT) $(RUNSIM)
-	rm -f tools-stamp proto-tools-stamp
+	rm -f tools-stamp proto-tools-stamp buf-stamp
 
-.PHONY: tools-clean statik runsim \
-	protoc-gen-gocosmos
+.PHONY: tools-clean statik runsim