fix #15005; [ARC] Global variable declared in a block is destroyed too…

[bung87]

… early

fix #15005.

now expand as below.

--expandArc: test

var
  b15005
  a15005`gensym0
var alreadyExecuted`gensym1 = false
if not alreadyExecuted`gensym1:
  alreadyExecuted`gensym1 = true
  `=sink`(a15005`gensym0, T(data: "hi"))
`=copy`(b15005, a15005`gensym0)
const
  loc`gensym3 = (filename: "t15005.nim", line: 15, column: 2)
  ploc`gensym3 = "t15005.nim(15, 3)"
bind instantiationInfo
mixin failedAssertImpl
{.line: (filename: "t15005.nim", line: 15, column: 2).}:
  if not (b15005.data == "hi"):
    failedAssertImpl("t15005.nim(15, 3) `b15005.data == \"hi\"` ")
`=destroy`(b15005)
-- end of expandArc ------------------------

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