ceedling linker flags

diff --git a/vendor/ceedling/lib/ceedling/defaults.rb b/vendor/ceedling/lib/ceedling/defaults.rb
--- a/vendor/ceedling/lib/ceedling/defaults.rb
+++ b/vendor/ceedling/lib/ceedling/defaults.rb
@@ -32,6 +32,7 @@
   :arguments => [
     "\"${1}\"".freeze,
     "-o \"${2}\"".freeze,
+    "-lm".freeze,
     ].freeze
   }