envsetup,product,ninja: enable symlink traversal

When searching device, product, or hardware, allow
find to follow symlinks.

Add KATI_EMULATE_FIND=false to allow disabling the find
emulator which changes findleaves.py behavior wrt
symlinks.

BUG=24605247
TEST=works with CL:783781 (without the find wrapper in that CL)

Change-Id: Ia9d0e4add391a56f34828a09a6cec3f435ccc548
diff --git a/core/envsetup.mk b/core/envsetup.mk
index 199c6b7..050d445 100644
--- a/core/envsetup.mk
+++ b/core/envsetup.mk
@@ -141,8 +141,8 @@
 board_config_mk := \
 	$(strip $(sort $(wildcard \
 		$(SRC_TARGET_DIR)/board/$(TARGET_DEVICE)/BoardConfig.mk \
-		$(shell test -d device && find device -maxdepth 4 -path '*/$(TARGET_DEVICE)/BoardConfig.mk') \
-		$(shell test -d vendor && find vendor -maxdepth 4 -path '*/$(TARGET_DEVICE)/BoardConfig.mk') \
+		$(shell test -d device && find -L device -maxdepth 4 -path '*/$(TARGET_DEVICE)/BoardConfig.mk') \
+		$(shell test -d vendor && find -L vendor -maxdepth 4 -path '*/$(TARGET_DEVICE)/BoardConfig.mk') \
 	)))
 ifeq ($(board_config_mk),)
   $(error No config file found for TARGET_DEVICE $(TARGET_DEVICE))