Update to get latest release from S3 (#15952)

* Update to get latest release from S3

* Update mmctl to download to use S3

* Download MMCTL from S3

* Update download_mmctl_release.sh

* Update Makefile

* Update release.mk

* Update the script called, remove call to sub shell and clean up indentation

* Add quotes around THIS_BRANCH var

* Update script to support overriding the OS for packaging

Co-authored-by: Mattermod <mattermod@users.noreply.github.com>

build/release.mk

@@ -97,8 +97,8 @@ package:
 	mkdir -p $(DIST_PATH)/client
 	cp -RL $(BUILD_WEBAPP_DIR)/dist/* $(DIST_PATH)/client
 
-	$(eval MMCTL_REL_TO_DOWNLOAD := $(shell scripts/get_latest_release.sh 'mattermost/mmctl' 'release-'))
-	@echo "Using mmctl version $(MMCTL_REL_TO_DOWNLOAD)"
+	@#Download MMCTL
+	scripts/download_mmctl_release.sh
 
 	@# Help files
 ifeq ($(BUILD_ENTERPRISE_READY),true)
@@ -133,7 +133,8 @@ else
 	cp $(GOBIN)/darwin_amd64/mattermost $(DIST_PATH)/bin # from cross-compiled bin dir
 	cp $(GOBIN)/darwin_amd64/platform $(DIST_PATH)/bin # from cross-compiled bin dir
 endif
-	MMCTL_FILE="darwin_amd64.tar" && curl -f -O -L https://github.com/mattermost/mmctl/releases/download/$(MMCTL_REL_TO_DOWNLOAD)/$$MMCTL_FILE && tar -xvf $$MMCTL_FILE -C $(DIST_PATH)/bin && rm $$MMCTL_FILE
+	#Download MMCTL for OSX
+	scripts/download_mmctl_release.sh "Darwin"
 	@# Prepackage plugins
 	@for plugin_package in $(PLUGIN_PACKAGES) ; do \
 		ARCH="osx-amd64"; \
@@ -167,7 +168,8 @@ else
 	cp $(GOBIN)/windows_amd64/mattermost.exe $(DIST_PATH)/bin # from cross-compiled bin dir
 	cp $(GOBIN)/windows_amd64/platform.exe $(DIST_PATH)/bin # from cross-compiled bin dir
 endif
-	MMCTL_FILE="windows_amd64.zip" && curl -f -O -L https://github.com/mattermost/mmctl/releases/download/$(MMCTL_REL_TO_DOWNLOAD)/$$MMCTL_FILE && unzip -o $$MMCTL_FILE -d $(DIST_PATH)/bin && rm $$MMCTL_FILE
+	#Download MMCTL for Windows
+	scripts/download_mmctl_release.sh "Windows"
 	@# Prepackage plugins
 	@for plugin_package in $(PLUGIN_PACKAGES) ; do \
 		ARCH="windows-amd64"; \
@@ -201,7 +203,8 @@ else
 	cp $(GOBIN)/linux_amd64/mattermost $(DIST_PATH)/bin # from cross-compiled bin dir
 	cp $(GOBIN)/linux_amd64/platform $(DIST_PATH)/bin # from cross-compiled bin dir
 endif
-	MMCTL_FILE="linux_amd64.tar" && curl -f -O -L https://github.com/mattermost/mmctl/releases/download/$(MMCTL_REL_TO_DOWNLOAD)/$$MMCTL_FILE && tar -xvf $$MMCTL_FILE -C $(DIST_PATH)/bin && rm $$MMCTL_FILE
+	#Download MMCTL for Linux
+	scripts/download_mmctl_release.sh "Linux"
 	@# Prepackage plugins
 	@for plugin_package in $(PLUGIN_PACKAGES) ; do \
 		ARCH="linux-amd64"; \