title: clang on windows (installed via scoop) is unable to find headers
body: <p>Trying to compile a simple hello world example using clang on windows fails and i dont know why since the command below displays locations that contain possible headers.</p>
  
  <pre><code>C:\Users\peter\Downloads&gt;clang-cl -v hello.c
  clang version 3.9.1 (branches/release_39)
  Target: x86_64-pc-windows-msvc
  Thread model: posix
  InstalledDir: C:\Users\peter\scoop\apps\llvm\current\bin
  "C:\\Users\\peter\\scoop\\apps\\llvm\\current\\bin\\clang-cl.exe" -cc1 -triple x86_64-pc-windows-msvc19.0.24215 -emit-obj -mrelax-all mincremental-linker-compatible -disable-free -disable-llvm-verifier -discard-value-names -main-file-name hello.c -mrelocation-model pic -pic-level 2 -mthread-model posix -relaxed-aliasing -fmath-errno -masm-verbose -mconstructor-aliases -munwind-tables -target-cpu x86-64 -D_MT -flto-visibility-public-std --dependent-lib=libcmt --dependent-lib=oldnames -stack-protector 2 -fms-volatile -fdiagnostics-format msvc -momit-leaf-frame-pointer -v -dwarf-column-info -debugger-tuning=gdb -resource-dir "C:\\Users\\peter\\scoop\\apps\\llvm\\current\\bin\\..\\lib\\clang\\3.9.1" -internal-isystem "C:\\Users\\peter\\scoop\\apps\\llvm\\current\\bin\\..\\lib\\clang\\3.9.1\\include" -internal-isystem "F:\\visualstudio2015\\VC\\include" -internal-isystem "C:\\Program Files (x86)\\Microsoft SDKs\\Windows\\v8.1A\\" -internal-isystem "C:\\Program Files (x86)\\Microsoft SDKs\\Windows\\v8.1A\\" -internal-isystem "C:\\Program Files (x86)\\Microsoft SDKs\\Windows\\v8.1A\\" -fdebug-compilation-dir "C:\\Users\\peter\\Downloads" -ferror-limit 19 -fmessage-length 120 -fms-extensions -fms-compatibility -fms-compatibility-version=19.0.24215 -fdelayed-template-parsing -fobjc-runtime=gcc -fdiagnostics-show-option -fcolor-diagnostics -o "C:\\Users\\peter\\AppData\\Local\\Temp\\hello-8512ad.obj" -x c hello.c
  clang -cc1 version 3.9.1 based upon LLVM 3.9.1 default target x86_64-pc-windows-msvc
  ignoring duplicate directory "C:\Program Files (x86)\Microsoft SDKs\Windows\v8.1A"
  ignoring duplicate directory "C:\Program Files (x86)\Microsoft SDKs\Windows\v8.1A"
  #include "..." search starts here:
  #include &lt;...&gt; search starts here:
  C:\Users\peter\scoop\apps\llvm\current\bin\..\lib\clang\3.9.1\include
  F:\visualstudio2015\VC\include
  C:\Program Files (x86)\Microsoft SDKs\Windows\v8.1A
  End of search list.
  hello.c(3,10):  fatal error: 'stdio.h' file not found
  #include &lt;stdio.h&gt;
       ^
  1 error generated.
  
  C:\Users\peter\Downloads&gt;
  </code></pre>
  
  <p>As the command shows i installed llvm from scoop eg <a href="http://scoop.sh/" rel="nofollow noreferrer">http://scoop.sh/</a> and tryed to compile code by simply calling clang.exe.</p>
  
  <p>i was looking at <a href="https://stackoverflow.com/questions/28980565/clang-on-windows-incorrect-header-file-path">clang on Windows - incorrect header file path</a></p>
  
  <p>and i can confirm that i dont have an environment variable named INCLUDE in either my user environment variables or my system environment variables</p>
  
  <p>running clang from inside the "VS2015 x64 Native Tools Command Prompt" shortcut seems to work (based upon just running "clang hello.c" from the downloads directory) however how do i apply whatever changes that shortcut makes to a currently running cmd prompt?</p>
  
  <p>The reason i'm not using cygwin/msys/mingw is because i believe them to be too heavy both diskspace-wise and complexity wise</p>