Move platform detection into docker Makefile

Author: cytopia

Makefile.docker

@@ -19,11 +19,19 @@ IMAGE   =
 # -------------------------------------------------------------------------------------------------
 NO_CACHE   =
 ARGS       =
-ARCH       = linux/amd64
 DOCKER_TAG = latest
 DIR        = .
 FILE       = Dockerfile
 
+# Auto-detect current platform and use it as default to build for
+_PLATFORM = $(shell uname -m)
+ifeq ($(strip $(_PLATFORM)),x86_64)
+	ARCH = linux/amd64
+else
+	ifeq ($(strip $(_PLATFORM)),arm64)
+		ARCH = linux/arm64
+	endif
+endif
 
 # -------------------------------------------------------------------------------------------------
 # Targets

Makefile.platform

@@ -12,7 +12,7 @@ ifneq (,)
 endif
 
 # Ensure additional Makefiles are present
-MAKEFILES = Makefile.docker Makefile.lint Makefile.platform
+MAKEFILES = Makefile.docker Makefile.lint
 $(MAKEFILES): URL=https://raw.githubusercontent.com/devilbox/makefiles/master/$(@)
 $(MAKEFILES):
 	@if ! (curl --fail -sS -o $(@) $(URL) || wget -O $(@) $(URL)); then \
@@ -27,7 +27,6 @@ include $(MAKEFILES)
 ```gitignore
 Makefile.docker
 Makefile.lint
-Makefile.platform
 ```