Add note about build-time flags for PAM support

[techknowlogick]

Fix #16639

[codecov-commenter]

Codecov Report

Merging #16641 (cdca5cf) into main (067d82b) will increase coverage by 0.00%.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             main   #16641   +/-   ##
=======================================
  Coverage   45.41%   45.41%           
=======================================
  Files         756      756           
  Lines       85247    85247           
=======================================
+ Hits        38713    38718    +5     
+ Misses      40271    40267    -4     
+ Partials     6263     6262    -1     

Impacted Files	Coverage Δ
modules/charset/charset.go	71.71% <0.00%> (-4.05%)	⬇️
modules/process/manager.go	75.30% <0.00%> (+2.46%)	⬆️
modules/queue/workerpool.go	55.72% <0.00%> (+2.67%)	⬆️

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