Use multiple "-t" to avoid multiple docker build calls

Author: larskanis

Rakefile

@@ -14,11 +14,9 @@ def build_mri_images(platforms, host_platforms, output: )
     sdf = "tmp/docker/Dockerfile.mri.#{platform}"
     image_name = RakeCompilerDock::Starter.container_image_name(platform: platform)
 
-    RakeCompilerDock.docker_build(sdf, tag: image_name, platform: plats, output: output)
-
-    if image_name.include?("linux-gnu")
-      RakeCompilerDock.docker_build(sdf, tag: image_name.sub("linux-gnu", "linux"), platform: plats, output: output)
-    end
+    tags = [image_name]
+    tags << image_name.sub("linux-gnu", "linux") if image_name.include?("linux-gnu")
+    RakeCompilerDock.docker_build(sdf, tag: tags, platform: plats, output: output)
   end
 end
 

build/parallel_docker_build.rb

@@ -25,7 +25,7 @@ def docker_build_cmd(platform=nil)
     def docker_build(filename, tag: nil, output: false, platform: )
       cmd = docker_build_cmd(platform)
       return if cmd.nil?
-      tag_args = ["-t", tag] if tag
+      tag_args = Array(tag).flat_map{|t| ["-t", t] } if tag
       push_args = ["--push"] if output == 'push'
       push_args = ["--load"] if output == 'load'
       Class.new.extend(FileUtils).sh(*cmd, "-f", filename, ".", "--platform", platform, *tag_args, *push_args)