doc: update for OS supported in C compilation flags (fix #26401) (#26406)

Author: lcheylus

doc/docs.md

@@ -7967,7 +7967,7 @@ C compilation line, before other libs), use:
 ```
 
 You can (optionally) use different flags for different targets.
-Currently the `linux`, `darwin` , `freebsd`, and `windows` flags are supported.
+Every OS listed in [Compile time code](#if-condition) is supported as flags.
 
 > [!NOTE]
 > Each flag must go on its own line (for now)