Disable threads for os:any (#21425)

config/nim.cfg

@@ -100,6 +100,11 @@ nimblepath="$home/.nimble/pkgs/"
   gcc.options.always %= "${gcc.options.always} -fsanitize=null -fsanitize-undefined-trap-on-error"
 @end
 
+# Turn off threads support when compiling for bare-metal targets (--os:any)
+@if any:
+  threads:off
+@end
+
 @if unix and mingw:
   # Cross compile for Windows from Linux/OSX using MinGW
   i386.windows.gcc.exe = "i686-w64-mingw32-gcc"

lib/std/typedthreads.nim

@@ -45,6 +45,8 @@ when defined(nimPreviewSlimSystem):
 when defined(genode):
   import genode/env
 
+when hostOS == "any":
+  {.error: "Threads not implemented for os:any. Please compile with --threads:off.".}
 
 when hasAllocStack or defined(zephyr) or defined(freertos) or defined(nuttx) or
     defined(cpu16) or defined(cpu8):