Directory.Build.props: set minimum Windows API version

Enforce a minimum Windows API version of build 16299 (aka '1709',
aka 'Redstone 3', aka 'Fall Creators Update'). This was the previous
target SDK version before 240f73e changed the native projects to
use the latest Windows SDK installed.

Setting the TargetPlatformMinVersion property for the native projects
will prevent use of APIs newer that the specified version, with newer
Windows SDKs.

Signed-off-by: Matthew John Cheetham <mjcheetham@outlook.com>

Author: mjcheetham

Directory.Build.props

@@ -34,6 +34,15 @@
     <OutDir>$(ProjectOutPath)bin\$(Platform)\$(Configuration)\</OutDir>
     <IntDir>$(ProjectOutPath)intermediate\$(Platform)\$(Configuration)\</IntDir>
     <GeneratedIncludePath>$(IntDir)include\</GeneratedIncludePath>
+    <!--
+      Make sure that we don't accidentally use Windows APIs only available after
+      Windows 10 build 16299 (aka '1709', 'RS3', and 'Fall Creators Update').
+      The minimum Windows version that includes the final design of the
+      Projected File System (ProjFS) APIs was actually Windows 10 version 1809
+      (build 17763), but VFS for Git also supports using the older design of the
+      ProjFS APIs from that version.
+    -->
+    <TargetPlatformMinVersion>10.0.16299.0</TargetPlatformMinVersion>
   </PropertyGroup>
 
 </Project>