CMAKE_INSTALL_PREFIX in Spanish on Windows

Code
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message("$ENV{ProgramFiles\(x86\)}")

gives a warning and doesn’t output what we want:

CMake Warning (dev) at D:/dev/CMExt/env_var.cmake:1 (message):
  Syntax error in cmake code at

    D:/dev/CMExt/env_var.cmake:1

  when parsing string

    $ENV{ProgramFiles\(x86\)}

  syntax error, unexpected cal_SYMBOL, expecting } (19)

  Policy CMP0010 is not set: Bad variable reference syntax is an error.  Run
  "cmake --help-policy CMP0010" for policy details.  Use the cmake_policy
  command to set the policy and suppress this warning.
This warning is for project developers.  Use -Wno-dev to suppress it.

$ENV{ProgramFiles\(x86\)}

cmake_policy(SET CMP0010 NEW)
message("$ENV{ProgramFiles\(x86\)}")

gives an error and stops processing:

CMake Error at D:/dev/CMExt/env_var.cmake:2 (message):
  Syntax error in cmake code at

    D:/dev/CMExt/env_var.cmake:2

  when parsing string

    $ENV{ProgramFiles\(x86\)}

  syntax error, unexpected cal_SYMBOL, expecting } (19)

cmake_policy(SET CMP0053 NEW)
message("$ENV{ProgramFiles\(x86\)}")

gives what we want:

C:\Program Files (x86)