chore: make it easier to override default profile

.gitignore

@@ -78,3 +78,4 @@ rebar-git-cache.tar
 .git/
 apps/emqx_utils/src/emqx_variform_parser.erl
 apps/emqx_utils/src/emqx_variform_scan.erl
+default-profile.mk

Makefile

@@ -23,6 +23,7 @@ endif
 export EMQX_DASHBOARD_VERSION ?= v1.9.0-beta.1
 export EMQX_EE_DASHBOARD_VERSION ?= e1.7.0-beta.9
 
+-include default-profile.mk
 PROFILE ?= emqx
 REL_PROFILES := emqx emqx-enterprise
 PKG_PROFILES := emqx-pkg emqx-enterprise-pkg