[cmake] Remove MSVC C4258 override

Tested on VS2017 and VS2019 llvm/clang builds with WX enabled - its no longer necessary to disable this warning.

Differential Revision: https://reviews.llvm.org/D67047

llvm-svn: 370866

Author: RKSimon

llvm/cmake/modules/HandleLLVMOptions.cmake

@@ -504,7 +504,6 @@ if (MSVC)
       -wd4146 # Suppress 'unary minus operator applied to unsigned type, result still unsigned'
       -wd4180 # Suppress 'qualifier applied to function type has no meaning; ignored'
       -wd4244 # Suppress ''argument' : conversion from 'type1' to 'type2', possible loss of data'
-      -wd4258 # Suppress ''var' : definition from the for loop is ignored; the definition from the enclosing scope is used'
       -wd4267 # Suppress ''var' : conversion from 'size_t' to 'type', possible loss of data'
       -wd4291 # Suppress ''declaration' : no matching operator delete found; memory will not be freed if initialization throws an exception'
       -wd4345 # Suppress 'behavior change: an object of POD type constructed with an initializer of the form () will be default-initialized'