document ARCH=

Signed-off-by: Bernhard Reutner-Fischer <rep.dot.nop@gmail.com>

Makefile.help

@@ -47,6 +47,7 @@ help:
 	@echo '  V=1			- Verbose build'
 	@echo '  V=2			- Very verbose build'
 	@echo '  CROSS=		- Override CROSS_COMPILER_PREFIX from .config'
+	@echo '  ARCH= 		- Use given arch for config targets'
 	@echo '  SHELL=		- Shell to use for make'
 	@echo '  CONFIG_SHELL=		- Shell to use for menuconfig'
 	@echo