make: support V=1 as short form of verbose=yes

make V=1 is commonly used for the purpose of trigger verboseness
across projects.

Change-Id: Id9dfb4a7eea8338b366ae8dadb56ab02ceabbb58

build/make/Makefile

@@ -74,7 +74,7 @@ HOSTCC?=gcc
 TGT_ISA:=$(word 1, $(subst -, ,$(TOOLCHAIN)))
 TGT_OS:=$(word 2, $(subst -, ,$(TOOLCHAIN)))
 TGT_CC:=$(word 3, $(subst -, ,$(TOOLCHAIN)))
-quiet:=$(if $(verbose),,yes)
+quiet:=$(if $(or $(verbose), $(V)),, yes)
 qexec=$(if $(quiet),@)
 
 # Cancel built-in implicit rules