ninja: add new package

This adds a host as well as a target package.

ninja.mk is provided to execute ninja.

The two patches have been taken from upstream to fix compile issues.

Signed-off-by: Andre Heider <a.heider@gmail.com>

devel/ninja/ninja.mk

@@ -0,0 +1,16 @@
+# To execute ninja from you package's Makefile:
+#
+# include ../../devel/ninja/ninja.mk
+#
+# define Build/Compile
+#   $(call Ninja,-C $(MY_NINJA_BUILD_DIR),$(MY_NINJA_ENV_VARS))
+# endef
+
+NINJA_ARGS:=$(filter -j%,$(filter-out -j,$(MAKEFLAGS)))
+ifneq ($(findstring c,$(OPENWRT_VERBOSE)),)
+  NINJA_ARGS+=-v
+endif
+
+define Ninja
+	$(2) $(STAGING_DIR_HOSTPKG)/bin/ninja $(NINJA_ARGS) $(1)
+endef