Bug Report

Current behavior

In some case, library archives generated thanks to dot_a_linkage=true are put into objs.a,
resulting in an archive file embedded into another archive file.

Example in ESP8266Audio CI:

• 1st .a generated by dot_a_linkage=true (log in CI)
• 2nd .a generated by arduino-builder (because of a too large number of generated files ?) (log in CI)
  ar cru p/libraries/ESP8266HTTPClient/objs.a p/libraries/ESP8266HTTPClient/ESP8266HTTPClient.a
• final error in CI

probable source: #961

Expected behavior

Any of the two, or both ?

• refuse to add .a archive files in AR command line.
• skip dot_a_linkage=true libraries ?

Environment

• CLI version (output of arduino-cli version):

arduino-builder shipped with arduino-ide-hourly-build

• OS and platform:

ubuntu / any