Fix packaging in Auditbeat (elastic#5104)

Was broken in elastic#5096 (part of elastic#5095), because p1/p2 files were introduced,
but they weren't used in the `before-build` setup.
(cherry picked from commit 5b6b2b6)

auditbeat/Makefile

@@ -9,26 +9,29 @@ TEST_ENVIRONMENT=false
 # This is called by the beats packer before building starts
 .PHONY: before-build
 before-build:
-	@cat ${ES_BEATS}/auditbeat/_meta/common.yml \
+	@cat ${ES_BEATS}/auditbeat/_meta/common.p1.yml \
 	     <(go run scripts/generate_config.go -os windows -concat) \
+	     ${ES_BEATS}/auditbeat/_meta/common.p2.yml \
 	     ${ES_BEATS}/libbeat/_meta/config.yml > \
 	     ${PREFIX}/${BEAT_NAME}-win.yml
 	@cat ${ES_BEATS}/auditbeat/_meta/common.reference.yml \
 	     <(go run scripts/generate_config.go -os windows -concat) \
 	     ${ES_BEATS}/libbeat/_meta/config.reference.yml > \
 	     ${PREFIX}/${BEAT_NAME}-win.reference.yml
 
-	@cat ${ES_BEATS}/auditbeat/_meta/common.yml \
+	@cat ${ES_BEATS}/auditbeat/_meta/common.p1.yml \
 	     <(go run scripts/generate_config.go -os darwin -concat) \
+	     ${ES_BEATS}/auditbeat/_meta/common.p2.yml \
 	     ${ES_BEATS}/libbeat/_meta/config.yml > \
 	     ${PREFIX}/${BEAT_NAME}-darwin.yml
 	@cat ${ES_BEATS}/auditbeat/_meta/common.reference.yml \
 	     <(go run scripts/generate_config.go -os darwin -concat) \
 	     ${ES_BEATS}/libbeat/_meta/config.reference.yml > \
 	     ${PREFIX}/${BEAT_NAME}-darwin.reference.yml
 
-	@cat ${ES_BEATS}/auditbeat/_meta/common.yml \
+	@cat ${ES_BEATS}/auditbeat/_meta/common.p1.yml \
 	     <(go run scripts/generate_config.go -os linux -concat) \
+	     ${ES_BEATS}/auditbeat/_meta/common.p2.yml \
 	     ${ES_BEATS}/libbeat/_meta/config.yml > \
 	     ${PREFIX}/${BEAT_NAME}-linux.yml
 	@cat ${ES_BEATS}/auditbeat/_meta/common.reference.yml \