Windows has this PATH environment variable length limit. Having many applications, SDKs will fill up to the limit very quickly. I was hoping that Windows 10 would fix this, but seems like it's still there.
One workaround is to use short name for directories. For example, "C:\Program Files" can be "C:\Progra~1", and "C:\Program Files (x86)" can be "C:\Progra~1". You can get the short name by issuing DOS command "dir /x".
Another difficulty is that it is not easy to edit the variable -- the dialog box's text field is way too small:
I've been using this utility called "Path Editor" and found it extremely useful:
Use this utility with DOS command "dir /x" to change the path with short names will reduce the PATH variable length.