Allow for falling back to msbuild 12 if msbuild 14 is not available (will build but not run)

Author: mmitche

build.cmd

@@ -4,17 +4,26 @@ SETLOCAL
 
 SET CACHED_NUGET=%LocalAppData%\NuGet\NuGet.exe
 SET SOLUTION_PATH=%~dp0src\CodeFormatter.sln
-SET BUILD_TOOLS_PATH="%ProgramFiles(x86)%\MSBuild\14.0\bin\MSBuild.exe"
+SET MSBUILD14_TOOLS_PATH="%ProgramFiles(x86)%\MSBuild\14.0\bin\MSBuild.exe"
+SET MSBUILD12_TOOLS_PATH="%ProgramFiles(x86)%\MSBuild\12.0\bin\MSBuild.exe"
+SET BUILD_TOOLS_PATH=%MSBUILD14_TOOLS_PATH%
 
-IF NOT EXIST %BUILD_TOOLS_PATH% (
-  echo In order to build or run this tool you need either Visual Studio 2015 or
+IF NOT EXIST %MSBUILD14_TOOLS_PATH% (
+  echo In order to run this tool you need either Visual Studio 2015 or
   echo Microsoft Build Tools 2015 tools installed.
   echo.
   echo Visit this page to download either:
   echo.
   echo http://www.visualstudio.com/en-us/downloads/visual-studio-2015-downloads-vs
   echo.
-  goto :eof
+  echo Attempting to fall back to MSBuild 12 for building only
+  echo.
+  IF NOT EXIST %MSBUILD12_TOOLS_PATH% (
+    echo Could not find MSBuild 12.  Please install build tools ^(See above^)
+    exit /b 1
+  ) else (
+    set BUILD_TOOLS_PATH=%MSBUILD12_TOOLS_PATH%
+  )
 )
 
 IF EXIST %CACHED_NUGET% goto restore
@@ -28,4 +37,4 @@ IF EXIST "%~dp0src\packages" goto build
 
 :build
 
-%BUILD_TOOLS_PATH% %SOLUTION_PATH% /p:OutDir="%~dp0bin " /nologo /m /v:m /flp:verbosity=normal %*
+%BUILD_TOOLS_PATH% %SOLUTION_PATH% /p:OutDir="%~dp0bin" /nologo /m /v:m /flp:verbosity=normal %*