Set OUT_DIR based on a common base path

Change-Id: I2c4ba8b101d4d186ed4b371b9d07b3bcf75bbcc9
Author: Jean-Baptiste Queru<jbq@google.com>
Signed-off-by: Bruce Beare <bruce.j.beare@intel.com>
diff --git a/core/envsetup.mk b/core/envsetup.mk
index c3ae3b0..e8c924e 100644
--- a/core/envsetup.mk
+++ b/core/envsetup.mk
@@ -133,7 +133,11 @@
 # figure out the output directories
 
 ifeq (,$(strip $(OUT_DIR)))
+ifeq (,$(strip $(OUT_DIR_COMMON_BASE)))
 OUT_DIR := $(TOPDIR)out
+else
+OUT_DIR := $(OUT_DIR_COMMON_BASE)/$(notdir $(PWD))
+endif
 endif
 
 DEBUG_OUT_DIR := $(OUT_DIR)/debug