Make default release mode build a "profiling" build

For the ability to profile our code with perf (and to generate the most readable flamegraphs) it is important to:

• Compile with -fno-omit-frame-pointer (unless the compiler already defaults to using this flag?)
• Compile with some debug symbols (unless you don't need detailed stack traces of your node module)

Doing this would move node-cpp-skel to doing a "profiling" build by default: https://github.com/mapbox/cpp/blob/master/glossary.md#profiling-build.

We can accomplish this by applying something like https://github.com/mapnik/node-mapnik/pull/804 to node-cpp-skel.

refs https://twitter.com/brendangregg/status/472869470675795968

检查仓库的默认 release-build 配置，然后将所请求的方法与 node-mapnik PR #804 进行比较。确认默认构建使用 -fno-omit-frame-pointer 并包含调试符号，并验证生成的 Node 模块仍可构建且适用于 perf 火焰图。