Add Visual Studio 2019 Community support (microsoft#74)

Author: patrick330602

build.bat

@@ -30,6 +30,10 @@ if exist "%ProgramFiles(x86)%\Microsoft Visual Studio\2019\Preview\MSBuild\Curre
     set MSBUILD="%ProgramFiles(x86)%\Microsoft Visual Studio\2019\Preview\MSBuild\Current\Bin\MSBuild.exe"
     goto :FOUND_MSBUILD
 )
+if exist "%ProgramFiles(x86)%\Microsoft Visual Studio\2019\Community\MSBuild\Current\Bin\MSBuild.exe" (
+    set MSBUILD="%ProgramFiles(x86)%\Microsoft Visual Studio\2019\Community\MSBuild\Current\Bin\MSBuild.exe"
+    goto :FOUND_MSBUILD
+)
 if exist "%ProgramFiles(x86)%\MSBuild\14.0\bin" (
     set MSBUILD="%ProgramFiles(x86)%\MSBuild\14.0\bin\msbuild.exe"
     goto :FOUND_MSBUILD