Before, mbed_app.json files were explicitly ignored when building tests.
This was mostly because you could have multiple mbed_app.json files in the
tree (for instance, in test case folders) and the behavior would be
undefined. Now the tools explicitly ensure that there aren't multiple
mbed_app.json files in your source files. So auto discovery of
mbed_app.json for testing is being reintroduced.
This addresses the issue where building tests via test.py always triggered
a clean build. This is because the mbed_config.h file was being deleted from
the shared OS build to ensure that the correct config was always being
used. However, this contanstly triggered a rebuild of the OS since the
config file was not present.
Due to the shared build, having multiple app configurations that could
override the OS settings is not possible. For this reason, we now ignore
app config files unless explicitly set via the command line option
'--app-config'. Though there will now be two mbed_config.h files in the
include path of the build, it shouldn't matter since the contents will be
the same.
Brian Daniels