PCbuild/build.bat: Add note about using msbuild response file. (python#1551)

char101 · zooba · commit 8619c5417ced · 2017-05-12T16:23:15.000-07:00
Using a response file will eliminate the headache associated with batch argument/quote processing.

For example I unsucessfully compiled python with visualcpptools when specifying VSInstallDir in the batch file (cannot find vcruntime.h)

```batch
build.bat -p x64 -e -M --no-tkinter  "/p:VCInstallDir=%VCInstallDir%"
```

but it build successfully when specifying it in a response file

msbuild.rsp:
```
/p:VCInstallDir=%VCInstallDir%
```
diff --git a/PCbuild/build.bat b/PCbuild/build.bat
@@ -10,7 +10,12 @@ echo.given.
 echo.
 echo.After the flags recognized by this script, up to 9 arguments to be passed
 echo.directly to MSBuild may be passed.  If the argument contains an '=', the
-echo.entire argument must be quoted (e.g. `%~nx0 "/p:PlatformToolset=v100"`)
+echo.entire argument must be quoted (e.g. `%~nx0 "/p:PlatformToolset=v100"`).
+echo.Alternatively you can put extra flags for MSBuild in a file named 
+echo.`msbuild.rsp` in the `PCbuild` directory, one flag per line. This file
+echo.will be picked automatically by MSBuild. Flags put in this file does not
+echo.need to be quoted. You can still use environment variables inside the 
+echo.response file.
 echo.
 echo.Available flags:
 echo.  -h  Display this help message
