sys: add _BSD_SOURCE 1 for compatibility reasons

[cHuberCoffee]

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[codecov]

Codecov Report

Merging #92 (bb66876) into master (22c3f7e) will not change coverage.
The diff coverage is n/a.

❗ Current head bb66876 differs from pull request most recent head 0219940. Consider uploading reports for the commit 0219940 to get more accurate results

@@           Coverage Diff           @@
##           master      #92   +/-   ##
=======================================
  Coverage   53.32%   53.32%           
=======================================
  Files         192      192           
  Lines       21477    21477           
=======================================
  Hits        11452    11452           
  Misses      10025    10025           

Impacted Files	Coverage Δ
src/sys/fs.c	30.76% <ø> (ø)
src/list/list.c	85.29% <0.00%> (-0.74%)	⬇️
src/fmt/print.c	88.00% <0.00%> (+0.30%)	⬆️

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