[Export] Missing flags for Seeeduino Arch Pro in Emblocks project.

[valeros]

Hello!
We have a small problem in platformio/platformio-core#508.
Looks like linker flags -u _printf_float and -u _scanf_float are missing in exported project for Emblocks, so printf doesn't work correctly with float values. Is this a bug?
Thanks!

[0xc0170]

This seems like a problem in the toolchain file, where for gcc: https://github.com/mbedmicro/mbed/blob/20948ad920372de6b5ff5bf2d4f2237f3730b470/workspace_tools/toolchains/gcc.py#L192 . The list seems to be not consistent, we shall have a look

cc @sg- @EmBlocks

[ciarmcom]

ARM Internal Ref: IOTMORF-217

[sg-]

Toolchain flags have been unified and are shared between a mbed tools and exported projects.