VS15: Add Visual Studio 15 generator

Call the generator "Visual Studio 15" without any year because the
preview version of VS 15 does not provide a year in the product name.

Copy cmGlobalVisualStudio14Generator to cmGlobalVisualStudio15Generator
and update version numbers accordingly.  Add the VS15 enumeration value.
Note that we do not need to add a MSVC15 variable or v150 toolset
because Visual Studio 15 comes with an updated version of the v140
toolset and remains ABI-compatible.

Teach tests VSExternalInclude, RunCMake.GeneratorPlatform, and
RunCMake.GeneratorToolset to treat VS 15 as they do VS 10-14.

Closes: #16143

1 files changed, 14 insertions, 0 deletions

diff --git a/Source/cmGlobalVisualStudio10Generator.cxx b/Source/cmGlobalVisualStudio10Generator.cxx
index ab87d67..8bb43ee 100644
--- a/Source/cmGlobalVisualStudio10Generator.cxx
+++ b/Source/cmGlobalVisualStudio10Generator.cxx
@@ -365,6 +365,20 @@ std::string cmGlobalVisualStudio10Generator::FindMSBuildCommand()
     }
   }
 
+  // Search where VS15Preview places it.
+  mskey = "HKEY_LOCAL_MACHINE\\SOFTWARE\\Microsoft\\VisualStudio\\SxS\\VS7;";
+  mskey += this->GetIDEVersion();
+  if (cmSystemTools::ReadRegistryValue(mskey.c_str(), msbuild,
+                                       cmSystemTools::KeyWOW64_32)) {
+    cmSystemTools::ConvertToUnixSlashes(msbuild);
+    msbuild += "/MSBuild/";
+    msbuild += this->GetIDEVersion();
+    msbuild += "/Bin/MSBuild.exe";
+    if (cmSystemTools::FileExists(msbuild, true)) {
+      return msbuild;
+    }
+  }
+
   msbuild = "MSBuild.exe";
   return msbuild;
 }