Quote MSBUILD_EXE and also use it

build/build.cmd

@@ -6,13 +6,13 @@ set MSBUILD_HOME=%WINDIR%\Microsoft.NET\Framework\v4.0.30319
 rem MSBuild project file is located in the same directory as the current script
 set MSBUILD_PROJECT=%~dp0\build.proj
 
-set MSBUILD_EXE=%MSBUILD_HOME%\msbuild.exe
+set MSBUILD_EXE="%MSBUILD_HOME%\msbuild.exe"
 
 rem verify whether the version of MSBuild that we need is installed
 if not exist %MSBUILD_EXE% goto msbuild_missing
 
 rem launch the build script
-call %MSBUILD_HOME%\msbuild.exe %MSBUILD_PROJECT% /verbosity:minimal /nologo
+call %MSBUILD_EXE% %MSBUILD_PROJECT% /verbosity:minimal /nologo
 if errorlevel 1 goto msbuild_failure
 goto :EOF