fixes Thread initializer for ARC/ORC on Macos

[ringabout]

Otherwise

2022-09-15T22:14:56.9592680Z /Users/runner/work/1/s/nimcache/tests/generics/tthread_generic.nim_4a8a08f09d37b73795649038408b5f33/@mtthread_generic.nim.c:100:101: error: scalar initializer cannot be empty
2022-09-15T22:14:56.9593710Z static NIM_CONST tyObject_Thread__zHU2p4cP5TKE0P9cAAcLY8g TM__4S7kGJlWA60L39cvweIkHuA_2 = {NIM_NIL, {}, NIM_NIL, {{(&NTIv2__Hlf80yaLZNgwpkXrygtUDA_)}, NIM_NIL, NIM_NIL}}

[ringabout]

posix.nim uses int type for all platforms:

type
  Pthread* {.importc: "pthread_t", header: "<sys/types.h>".} = int

[ringabout]

Regarding the reason why it is specific to ARC/ORC is that ARC/ORC initializes the Thread object using const initializer while the importc symbol has the wrong types.

  of frEmbedded:
    # inheritance in C++ does not allow struct initialization: bug #18410
    if not p.module.compileToCpp and optTinyRtti in p.config.globalOptions:
      var tmp: TLoc
      if mode == constructRefObj:
        let objType = t.skipTypes(abstractInst+{tyRef})
        rawConstExpr(p, newNodeIT(nkType, a.lode.info, objType), tmp)
        linefmt(p, cpsStmts,
            "#nimCopyMem((void*)$1, (NIM_CONST void*)&$2, sizeof($3));$n",
            [rdLoc(a), rdLoc(tmp), getTypeDesc(p.module, objType, mapTypeChooser(a))])
      else:
        rawConstExpr(p, newNodeIT(nkType, a.lode.info, t), tmp)
        genAssignment(p, a, tmp, {})

And pthread_t is a pointer which should not be initialized by bracket expression.

typedef struct _opaque_pthread_t *__darwin_pthread_t;

Either ARC/ORC doesn't use static const to initialize importc objects or importc objects should have a right Nim type.

It should be related to #18844

[github-actions]

Thanks for your hard work on this PR!
The lines below are statistics of the Nim compiler built from f6dc30e

Hint: mm: orc; threads: on; opt: speed; options: -d:release
164220 lines; 12.675s; 842.504MiB peakmem