Fix frcmake.bat for install paths with spaces

If you install the toolchain for Windows to a path that has a space in it (such as C:\Program Files (x86)\FRC Toolchain), the batch script will interpret only the path up to the space as the program to run, and will fail with a message like "'C:\Program' is not recognized as an internal or external command, operable program or batch file." Quoting %CMAKE% forces Windows to follow the whole path.