build: make ninja build respect V=

Compiling with `make V=1` (which is the default) now runs ninja in
 verbose mode. To disable, run `make V=`.

Makefile

@@ -14,6 +14,12 @@ NODE ?= ./node
 # or set the V environment variable to an empty string.
 V ?= 1
 
+ifeq ($(USE_NINJA),1)
+ifneq ($(V),)
+NINJA := $(NINJA) -v
+endif
+endif
+
 # BUILDTYPE=Debug builds both release and debug builds. If you want to compile
 # just the debug build, run `make -C out BUILDTYPE=Debug` instead.
 ifeq ($(BUILDTYPE),Release)