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/main.mk b/core/main.mk
index 59e9524..3720971 100644
--- a/core/main.mk
+++ b/core/main.mk
@@ -457,6 +457,9 @@
 $(error The 'sdk' target may not be specified with any other targets)
 endif
 
+# AUX dependencies are already added by now; remove triggers from the MAKECMDGOALS
+MAKECMDGOALS := $(strip $(filter-out AUX-%,$(MAKECMDGOALS)))
+
 # TODO: this should be eng I think.  Since the sdk is built from the eng
 # variant.
 tags_to_install := debug eng
@@ -934,6 +937,8 @@
 all_modules: $(my_all_modules)
 endif
 
+.PHONY: auxiliary
+auxiliary: $(INSTALLED_AUX_TARGETS)
 
 # Build files and then package it into the rom formats
 .PHONY: droidcore