Exclude predefined variables from board config

mk2rbc has a few predefined variables that can't be
set in the product/board config makefiles, unless they're
set to their predefined values. Exclude these variables
from the board config input variables so that they don't
conflict.

Bug: 201700692
Test: m RBC_BOARD_CONFIG=1 mainline_system_x86_64-userdebug (ninja files differ still but this fixes a compilation error)
Change-Id: Idc11b2c5029d28116236b289ad1f09afaaf83cc3
diff --git a/core/board_config.mk b/core/board_config.mk
index 120f511..15a9944 100644
--- a/core/board_config.mk
+++ b/core/board_config.mk
@@ -191,7 +191,7 @@
 define dump-public-variables
 $(file >$(OUT_DIR)/dump-public-variables-temp.txt,$(subst $(space),$(newline),$(.VARIABLES)))\
 $(file >$(1),\
-$(foreach v, $(shell grep -he "^[A-Z][A-Z0-9_]*$$" $(OUT_DIR)/dump-public-variables-temp.txt | grep -vhe "^SOONG_"),\
+$(foreach v, $(shell grep -he "^[A-Z][A-Z0-9_]*$$" $(OUT_DIR)/dump-public-variables-temp.txt | grep -vhE "^(SOONG_.*|LOCAL_PATH|TOPDIR|PRODUCT_COPY_OUT_.*)$$"),\
 $(v) := $(strip $($(v)))$(newline)))
 endef