Starting in R2014a, the installer automatically tries to download the installation files to the Downloads folder (Windows) or your Home directory (Linux/Mac).If you have size limitations on either directory, you can change the default download directory by passing a -downloadFolder flag to the install script.
On Windows, and example command would look like this:
"C:\Users\Username\Downloads\MATLAB_R2017a\setup.exe" -downloadFolder "D:\Program Files\MATLAB\Downloads"
Alter the file paths in the command above to match where the setup.exe file is located, and where you would like the download folder to be.
On Linux or Mac OS X, this command would look like:
./install -downloadFolder /tmp/MathWorks