Merge pull request #67 from microbit-carlos/gcc-opt

Suggestion: Increase GCC optimisation level to Os (optimise for size).

Author: flit

records/tools/make_gcc_arm.yaml

@@ -15,7 +15,7 @@ tool_specific:
                 - c
                 - nosys
             common_flags:
-                - -O0
+                - -Os
                 - -Wall
                 - -ffunction-sections
                 - -fdata-sections