Modify BOM test

test/CMakeLists.txt

@@ -30,7 +30,7 @@ if(WIN32)
 FILE(WRITE ${CMAKE_CURRENT_BINARY_DIR}/test_helper.ps1
 "if (Test-Path $args[2]) { Remove-Item -Force $args[2] } \n"
 "$ErrorActionPreference = \"Stop\"\n"
-"If ((Get-Content $args[1] | & file - | %{$_ -match \"BOM\"}) -contains $true) {\n"
+"If ((Get-Content $args[1] | %{$_ -match \"\\xEF\\xBB\\xBF\" }) -contains $true) {\n"
 "echo 'Skipped due to wrong input encoding'\n"
 "exit 0\n"
 "}\n"