Add BUILD_BROKEN_USES_NETWORK

Some people apparently still talk to the network during their build.
Allow this temporarily with a BUILD_BROKEN_USES_NETWORK check.

Bug: 129992021
Test: attempt to talk to the network during the build with and without
      this flag
Change-Id: I45612ad6165f92f123847b4057338c0dfc3424ee
diff --git a/core/board_config.mk b/core/board_config.mk
index ed741c3..6f04fb3 100644
--- a/core/board_config.mk
+++ b/core/board_config.mk
@@ -89,6 +89,7 @@
   BUILD_BROKEN_DUP_RULES \
   BUILD_BROKEN_PHONY_TARGETS \
   BUILD_BROKEN_ENG_DEBUG_TAGS \
+  BUILD_BROKEN_USES_NETWORK \
 
 _board_true_false_vars := $(_build_broken_var_list)
 _board_strip_readonly_list += $(_build_broken_var_list)
@@ -101,11 +102,7 @@
 # ###############################################################
 # Broken build defaults
 # ###############################################################
-BUILD_BROKEN_ANDROIDMK_EXPORTS :=
-BUILD_BROKEN_DUP_COPY_HEADERS :=
-BUILD_BROKEN_DUP_RULES :=
-BUILD_BROKEN_PHONY_TARGETS :=
-BUILD_BROKEN_ENG_DEBUG_TAGS :=
+$(foreach v,$(_build_broken_var_list),$(eval $(v) :=))
 
 # Boards may be defined under $(SRC_TARGET_DIR)/board/$(TARGET_DEVICE)
 # or under vendor/*/$(TARGET_DEVICE).  Search in both places, but