introduce AUX build class of targets

AUX is a new class, similar to TARGET
While TARGET defines toolchain for Application Processors
AUX is defining toolchains for arbitrary utility cores (DSPs, GPUs,
MCUs, etc). This allows building of non-android sources as part
of Android tree and avoid using prebuilts if source code is avaliable

Bug: 29635686
Change-Id: Ie755ea054b16c3e86369f5fb2ba6eb0b384af77f
Signed-off-by: Alexey Polyudov <apolyudov@google.com>
diff --git a/core/ninja.mk b/core/ninja.mk
index 62102ba..069a43e 100644
--- a/core/ninja.mk
+++ b/core/ninja.mk
@@ -17,6 +17,7 @@
 	DUMP_% \
 	ECLIPSE-% \
 	PRODUCT-% \
+	AUX-% \
 	boottarball-nodeps \
 	brillo_tests \
 	btnod \