dot_a_linkage causes compilation trouble

[MCUdude]

See MCUdude/MightyCore#135 for details.

In short terms, I'm experiencing build issues when a library (SPI and Wire in this case) has dot_a_linkage=true.

[facchinm]

@MCUdude @per1234 thanks for the extensive debugging of the issue on the other thread. The order of .o files is not defined and depends on the lib discovery order because it's normally a non issue.
This line prevents the builder from knowing if the object is an archive or a .o, so we cannot reorder the list in a later stage.

I'll try to think about a workaround, but it looks the only way would be to keep two lists and merge in the correct order at link time.