message: build: reference bpowers/Heap-Layers
diff: [submodule "Heap-Layers"]
  path = src/vendor/Heap-Layers
  - url = https://github.com/emeryberger/Heap-Layers
  + url = https://github.com/bpowers/Heap-Layers
  [submodule "src/vendor/gflags"]
  path = src/vendor/gflags
  url = https://github.com/gflags/gflags.git
  