build: Honour NO_COLOR in include/scan.mk

build: Honour NO_COLOR in include/scan.mk

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Hi all:

This is my first OpenWrt patch. I am a clean, pure newbie! 8-)

Honour NO_COLOR in Makefile function 'progress' in include/scan.mk, in the same way that include/verbose.mk does.

Signed-off-by: R. Diez <rdiezmail-openwrt@yahoo.com>