title: Why can't Qt Creator find the Windows 10 SDK headers?
body: <p>I've installed Qt 5.14.2 with 64-bit MSVC libraries and Qt Creator 4.12.1. When I attempt to build any of the example projects, I get the following error:</p>
  
  <pre><code>C1083: Cannot open include file: 'stddef.h': No such file or directory.
  </code></pre>
  
  <p>I've already installed Visual Studio, along with UCRT and the Windows 10 SDK. I've verified that <code>stddef.h</code> does in fact exist inside the SDK. The problem appears to be that <code>vcvarsall.bat</code> (or <code>vcvars64.bat</code>) does not add the include directories for the SDK.</p>
  
  <p>Here are the environment variables that are assigned by <code>vcvars64.bat</code>:</p>
  
  <pre><code>CommandPromptType=Native                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                
  DevEnvDir=C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\Common7\IDE\
  ExtensionSdkDir=C:\Program Files (x86)\Microsoft SDKs\Windows Kits\10\ExtensionSDKs
  Framework40Version=v4.0
  FrameworkDir=C:\Windows\Microsoft.NET\Framework64\
  FrameworkDir64=C:\Windows\Microsoft.NET\Framework64\
  FrameworkVersion=v4.0.30319
  FrameworkVersion64=v4.0.30319
  INCLUDE=C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\VC\Tools\MSVC\14.26.28801\ATLMFC\include;C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\VC\Tools\MSVC\14.26.28801\include;
  LIB=C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\VC\Tools\MSVC\14.26.28801\ATLMFC\lib\x64;C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\VC\Tools\MSVC\14.26.28801\lib\x64;
  LIBPATH=C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\VC\Tools\MSVC\14.26.28801\ATLMFC\lib\x64;C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\VC\Tools\MSVC\14.26.28801\lib\x64;C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\VC\Tools\MSVC\14.26.28801\lib\x86\store\references;C:\Windows\Microsoft.NET\Framework64\v4.0.30319;
  Path=C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\Common7\IDE\\Extensions\Microsoft\IntelliCode\CLI;C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\VC\Tools\MSVC\14.26.28801\bin\HostX64\x64;C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\Common7\IDE\VC\VCPackages;C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\Common7\IDE\CommonExtensions\Microsoft\TestWindow;C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\Common7\IDE\CommonExtensions\Microsoft\TeamFoundation\Team Explorer;C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\MSBuild\Current\bin\Roslyn;C:\Program Files (x86)\Microsoft Visual…
  Platform=x64
  VCIDEInstallDir=C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\Common7\IDE\VC\
  VCINSTALLDIR=C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\VC\
  VCToolsInstallDir=C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\VC\Tools\MSVC\14.26.28801\
  VCToolsRedistDir=C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\VC\Redist\MSVC\14.26.28720\
  VCToolsVersion=14.26.28801
  VisualStudioVersion=16.0
  VS160COMNTOOLS=C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\Common7\Tools\
  VSCMD_ARG_app_plat=Desktop
  VSCMD_ARG_HOST_ARCH=x64
  VSCMD_ARG_TGT_ARCH=x64
  VSCMD_VER=16.6.0
  VSINSTALLDIR=C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\
  WindowsLibPath=References\CommonConfiguration\Neutral
  WindowsSDKLibVersion=winv6.3\
  WindowsSDKVersion=\
  __DOTNET_ADD_64BIT=1
  __DOTNET_PREFERRED_BITNESS=64
  __VSCMD_PREINIT_PATH=C:\Program Files (x86)\Common Files\Oracle\Java\javapath;C:\ProgramData\Oracle\Java\javapath;C:\windows\system32;C:\windows;C:\windows\System32\Wbem;C:\windows\System32\WindowsPowerShell\v1.0\;C:\windows\System32\OpenSSH\;C:\Program Files\Perforce;C:\Program Files\ServiceNow;C:\Program Files\PuTTY\;C:\Program Files\PowerShell\7\;C:\Program Files\Git\cmd;C:\Program Files\Microsoft SQL Server\130\Tools\Binn\;C:\Program Files\dotnet\;C:\Program Files\nodejs\;C:\Users\[REDACTED]\AppData\Local\Microsoft\WindowsApps;;C:\Users\[REDACTED]\AppData\Local\Programs\Microsoft VS Code\bin;C:\Users\[REDACTED]\AppData\Roaming\npm
  __VSCMD_script_err_count=0
  </code></pre>
  
  <p><code>stddef.h</code> is in <code>C:\Program Files (x86)\Windows Kits\10\Include\10.0.18362.0\ucrt</code>, but that path is not added to <code>INCLUDE</code>.</p>
  
  <p>How is Qt Creator supposed to find the Windows SDK?</p>