Comment (by Roland Haas):

gcc -print-search-dirs will output some more than just the “system” directories since it includes gcc specific locations beyond what eg ld- v reports and also the ones from LIBRARY_PATH it seems. Which should be find since LIBRARY_PATH is late in the search order compared to -L.

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Ticket URL: https://bitbucket.org/einsteintoolkit/tickets/issues/2532/try-and-auto-detect-system-directories-to