[CMake] Always mark terminfo as unavailable on Windows

[phosek]

Summary

This addresses the issue introduced by D86134.

llvm/cmake/config-ix.cmake

if((LLVM_ENABLE_LIBXML2) AND ((CMAKE_SYSTEM_NAME MATCHES "Linux") AND (ICONV_LIBRARY_PATH) OR APPLE))
         set(LLVM_LIBXML2_ENABLED 1)
         if ((CMAKE_OSX_SYSROOT) AND (EXISTS ${CMAKE_OSX_SYSROOT}/${LIBXML2_INCLUDE_DIR}))
           include_directories(${CMAKE_OSX_SYSROOT}/${LIBXML2_INCLUDE_DIR})
         else()
           include_directories(${LIBXML2_INCLUDE_DIR})
         endif()
       endif()
     endif()
+  else()
+    set(LLVM_ENABLE_TERMINFO 0)
   endif()
 endif()
 
 if (LLVM_ENABLE_LIBXML2 STREQUAL "FORCE_ON" AND NOT LLVM_LIBXML2_ENABLED)
   message(FATAL_ERROR "Failed to congifure libxml2")
 endif()
 
 check_library_exists(xar xar_open "" HAVE_LIBXAR)