Update name of Sandcastle Help File Builder environment variable.

build/sandcastle/SSH.NET.shfbproj

@@ -36,7 +36,7 @@
   <outputPaths>{@HelpFormatOutputPaths}</outputPaths>
   <allowMissingSource value="false" />
   <removeRegionMarkers value="false" />
-  <colorizer syntaxFile="{@SHFBFolder}PresentationStyles\Colorizer\highlight.xml" styleFile="{@SHFBFolder}PresentationStyles\Colorizer\highlight.xsl" stylesheet="{@SHFBFolder}PresentationStyles\Colorizer\highlight.css" scriptFile="{@SHFBFolder}PresentationStyles\Colorizer\highlight.js" disabled="{@DisableCodeBlockComponent}" language="cs" tabSize="0" numberLines="false" outlining="false" keepSeeTags="false" defaultTitle="true" />
+  <colorizer syntaxFile="{@SHFBROOT}PresentationStyles\Colorizer\highlight.xml" styleFile="{@SHFBROOT}PresentationStyles\Colorizer\highlight.xsl" stylesheet="{@SHFBROOT}PresentationStyles\Colorizer\highlight.css" scriptFile="{@SHFBROOT}PresentationStyles\Colorizer\highlight.js" disabled="{@DisableCodeBlockComponent}" language="cs" tabSize="0" numberLines="false" outlining="false" keepSeeTags="false" defaultTitle="true" />
 </component>
       </ComponentConfig>
     </ComponentConfigurations>
@@ -72,5 +72,5 @@
   <PropertyGroup Condition=" '$(Configuration)|$(Platform)' == 'Release|Win32' ">
   </PropertyGroup>
   <!-- Import the SHFB build targets -->
-  <Import Project="$(SHFBFolder)\SandcastleHelpFileBuilder.targets" />
+  <Import Project="$(SHFBROOT)\SandcastleHelpFileBuilder.targets" />
 </Project>