Detect if we are building for RPI so we can push to raspbian.

support/ohai-helper

@@ -23,7 +23,7 @@ def repo_string
       version = 'xenial'
     end
   when 'debian', 'raspbian'
-    os = ohai['platform']
+    os = verify_platform
     case ohai['platform_version']
     when /^7\./
       version = 'wheezy'
@@ -56,6 +56,19 @@ def ohai
   end.data
 end
+def verify_platform
+  # We have no way to verify whether we are building for RPI
+  # as the builder machine will report that it is Debian.
+  # Since we don't officially release  arm packages, it should be safe to
+  # assume that if we are on a Debian machine on arm, we are building for
+  # Raspbian.
+  if ohai['kernel']['machine'] =~ /armv/
+    'raspbian'
+  else
+    ohai['platform']
+  end
+end
+
 case ARGV.first
 when 'platform-dir'
   platform_dir