make_gcc_arm exporter fails for online compiler

[bentcooke]

Using NUCLEO_F411RE, the make_gcc_arm exporter fails with the following:

[janjongboom]

Tracking here ARMmbed/mbed-os#6395.

[ciarmcom]

ARM Internal Ref: IOTCELL-771

[kivaisan]

Closing this issue as tracked with other issue.