Build with `-fno-threadsafe-statics`

[arodland]

What kind of issue is this?

• Feature Request. Start by telling us what problem you’re trying to solve. Often a solution
  already exists! Don’t send pull requests to implement new features without first getting our
  support. Sometimes we leave features out on purpose to keep the project small.

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It looks like you should add -fno-threadsafe-statics to the default build flags. I ported an Arduino Due project to platform.io and the build size got twice as big. On some investigation I found that a whole mess of exception handling code was being included (despite -fno-exceptions) with pio that wasn't included when building with arduino. I tracked it down to FrameworkArduino/USB/PluggableUSB.cpp, specifically the static PluggableUSB_ obj; line, which brings in __cxa_guard_acquire, which brings in the whole rest of the mess. Adding build_flags = -fno-threadsafe-statics in my platformio.ini brings the text size down from 89776 to 40208. The Arduino IDE builds with this flag since 1.5.8 (arduino/Arduino#107).

[valeros]

Thanks! Fixed in development version.