enable --tlsEmulation:on for --gc:arc (#13685)

* enable --tlsEmulation:on for --gc:arc
* make -d:useMalloc work with --gc:arc --threads:on

lib/system/memalloc.nim

@@ -339,7 +339,7 @@ when defined(js):
   proc reallocShared0(p: pointer, oldsize, newsize: Natural): pointer = discard
 
 
-when hasAlloc and hasThreadSupport:
+when hasAlloc and hasThreadSupport and not defined(useMalloc):
   proc getOccupiedSharedMem*(): int {.rtl.}
     ## Returns the number of bytes that are owned by the process
     ## on the shared heap and hold data. This is only available when

lib/system/mm/malloc.nim

@@ -75,6 +75,6 @@ proc alloc(r: var MemRegion, size: int): pointer =
 proc alloc0Impl(r: var MemRegion, size: int): pointer =
   result = alloc0Impl(size)
 proc dealloc(r: var MemRegion, p: pointer) = dealloc(p)
-proc deallocOsPages(r: var MemRegion) {.inline.} = discard
-proc deallocOsPages() {.inline.} = discard
+proc deallocOsPages(r: var MemRegion) = discard
+proc deallocOsPages() = discard
 

lib/system/threads.nim

@@ -79,7 +79,7 @@ when not defined(useNimRtl):
 # use ``stdcall`` since it is mapped to ``noconv`` on UNIX anyway.
 
 type
-  Thread* {.pure, final.}[TArg] = object
+  Thread*[TArg] = object
     core: PGcThread
     sys: SysThread
     when TArg is void:
@@ -98,9 +98,6 @@ proc onThreadDestruction*(handler: proc () {.closure, gcsafe.}) =
   ## A thread is destructed when the ``.thread`` proc returns
   ## normally or when it raises an exception. Note that unhandled exceptions
   ## in a thread nevertheless cause the whole process to die.
-  when not defined(nimNoNilSeqs):
-    if threadDestructionHandlers.isNil:
-      threadDestructionHandlers = @[]
   threadDestructionHandlers.add handler
 
 template afterThreadRuns() =