Let arduino-cli decide library specification

[ianfixes]

Demonstrates a possible bug in arduino-cli

[ianfixes]

Depends on arduino/arduino-cli#1092 I think

[hlovdal]

Reading the discussion, would it not make sense to create four test repositories under https://github.com/Arduino-CI/ to have some known reference points to use for testing this? E.g.

FooLibLegacy1
|_ FooLib1.h

FooLibLegacy2
|_ src
    |_ FooLib2.h

FooLibNonLegacy3
|_ library.properties
|_ FooLib3.h

FooLibNonLegacy4
|_ library.properties
|_ src
    |_ FooLib4.h

[ianfixes]

@hlovdal I do have something resembling that already:

• https://github.com/Arduino-CI/arduino_ci/tree/master/SampleProjects/OnePointOhDummy
• https://github.com/Arduino-CI/arduino_ci/tree/master/SampleProjects/OnePointFiveDummy
• https://github.com/Arduino-CI/arduino_ci/tree/master/SampleProjects/OnePointFiveMalformed