Description

Some application fails when using BUILD_IN_DOCKER as they are using unavailable host toolchain. (#11083)
However, when compiling for all boards using `buildtest' it hides the error as the whole process is run in docker.

Fixing

Removing the special docker handling for buildtest should fix the issue.

Steps to reproduce the issue

I have my arm-gcc path in /opt so overwriting my path as the example removes it

As reference, this should fail:

DOCKER="sudo docker" BOARD=nrf52dk BOARDS=nrf52dk PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin  BUILD_IN_DOCKER=1 make -C tests/mcuboot/ all

The issue is shown with buildtest that should give the same result:

DOCKER="sudo docker" BOARD=nrf52dk BOARDS=nrf52dk PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin  BUILD_IN_DOCKER=1 make -C tests/mcuboot/ buildtest

Expected results

Building for nrf52dk ... failed!

Actual results

Building for nrf52dk ... success.

Versions

The issue and failing test case is available in https://github.com/RIOT-OS/RIOT/releases/tag/2019.07-RC1

Found during release testing RIOT-OS/Release-Specs#128