Windows ToolChain: remove excessive backslash if we find WindowsSDK

[akuharev]

Summary

Previously we had:
clang -cc1 ... double backslash in windowsSDK include

Excessive backslash is returned by function getWindowsSDKDir.
The Windows registry contains Microsoft InstallDir with trailing backslash.

[yaron.keren]

I 'm not sure the problem is here. The sys::path::append function knows how to deal with duplicate slashes so if you do get duplicate backslash, plain string concatenation was probably used instead of sys::path::append. In such case the correct bug fix would be to use sys::path::append instead of the string concatenation.

[rnk]

Thanks for the info, this should be fixed in r206933.

BTW, I recommend not relying on that registry searching code. It's not well
maintained. The best way to make sure you're getting the right VC and SDK
headers is to set INCLUDE in the environment, most likely with
vcvarsall.bat.

lib/Driver/WindowsToolChain.cpp

static bool getWindowsSDKDir(std::string &path) {
   // Try the Windows registry.
   bool hasSDKDir = getSystemRegistryString(
    "HKEY_LOCAL_MACHINE\\SOFTWARE\\Microsoft\\Microsoft SDKs\\Windows\\$VERSION",
                                            "InstallationFolder",
                                            windowsSDKInstallDir,
                                            sizeof(windowsSDKInstallDir) - 1);
     // If we have both vc80 and vc90, pick version we were compiled with.
   if (hasSDKDir && windowsSDKInstallDir[0]) {
+    char *p = windowsSDKInstallDir + strlen(windowsSDKInstallDir) - 1;
+    if (*p == '\\')
+      *p = '\0';
     path = windowsSDKInstallDir;
     return true;
   }
   return false;
 }
 
   // Get Visual Studio installation directory.
 static bool getVisualStudioDir(std::string &path) {