Split to multiple bash commands.

This can fix the error "/bin/bash: Argument list too long", if we get a
really long apk list.
Bug tracker Link: http://code.google.com/p/android/issues/detail?id=38937

Change-Id: I72258125c4297dfd9f8f502a96dbfa5a08f3cc50
diff --git a/core/Makefile b/core/Makefile
index 4e547ad..1a816e5 100644
--- a/core/Makefile
+++ b/core/Makefile
@@ -240,6 +240,12 @@
 
 # -----------------------------------------------------------------
 # Cert-to-package mapping.  Used by the post-build signing tools.
+# Use a macro to add newline to each echo command
+define _apkcerts_echo_with_newline
+$(hide) echo $(1)
+
+endef
+
 name := $(TARGET_PRODUCT)
 ifeq ($(TARGET_BUILD_TYPE),debug)
   name := $(name)_debug
@@ -254,13 +260,15 @@
 	@echo APK certs list: $@
 	@mkdir -p $(dir $@)
 	@rm -f $@
-	$(hide) $(foreach p,$(PACKAGES),\
-          $(if $(PACKAGES.$(p).EXTERNAL_KEY),\
-	    echo 'name="$(p).apk" certificate="EXTERNAL" \
-	         private_key=""' >> $@;,\
-	    echo 'name="$(p).apk" certificate="$(PACKAGES.$(p).CERTIFICATE)" \
-	         private_key="$(PACKAGES.$(p).PRIVATE_KEY)"' >> $@;))
-	# In case $(PACKAGES) is empty.
+	$(foreach p,$(PACKAGES),\
+	  $(if $(PACKAGES.$(p).EXTERNAL_KEY),\
+	    $(call _apkcerts_echo_with_newline,\
+	      'name="$(p).apk" certificate="EXTERNAL" \
+	      private_key=""' >> $@),\
+	    $(call _apkcerts_echo_with_newline,\
+	      'name="$(p).apk" certificate="$(PACKAGES.$(p).CERTIFICATE)" \
+	      private_key="$(PACKAGES.$(p).PRIVATE_KEY)"' >> $@)))
+	# In case value of PACKAGES is empty.
 	$(hide) touch $@
 
 .PHONY: apkcerts-list