lib/logger: explicitly import "time/tzdata" package for embedding tzdata into the app

The approach with `timetzdata` build tag didn't work for GOARCH=arm and GOARCH=ppc64le
due to the issue https://github.com/golang/go/issues/44073#issuecomment-778854298

deployment/docker/Makefile

@@ -34,7 +34,7 @@ app-via-docker: package-builder
 		$(BUILDER_IMAGE) \
 		go build $(RACE) -mod=vendor -trimpath \
 			-ldflags "-extldflags '-static' $(GO_BUILDINFO)" \
-			-tags 'netgo osusergo nethttpomithttp2 timetzdata' \
+			-tags 'netgo osusergo nethttpomithttp2' \
 			-o bin/$(APP_NAME)$(APP_SUFFIX)-prod $(PKG_PREFIX)/app/$(APP_NAME)
 
 package-via-docker: package-base

lib/logger/tzdata.go

@@ -0,0 +1,9 @@
+// +build go1.15
+
+package logger
+
+import (
+	// This is needed for embedding tzdata into binary, so `-loggerTimezone` could work in an app running on a scratch base Docker image.
+	// The "time/tzdata" package has been appeared starting from Go1.15 - see https://golang.org/doc/go1.15#time/tzdata
+	_ "time/tzdata"
+)