Fixing UpdateH5 logic in Sdk.targets

[mjrist]

It was not possible to set UpdateH5 to false to disable the update of the global h5 compiler when not using the compilation server.

This change updates the checks to make this possible.

Summary of the updated behavior:

If using the global compiler and it is not installed, UpdateH5 gets set to true so that it gets installed. (Now this simply calls h5 instead of h5 check-if-online which would return non-zero if the server was not running even though h5 was installed.)

If using the global compiler and it is installed, then do whatever is indicated by UpdateH5.

• UpdateH5 is set to true by default to keep the existing behavior of checking for updates when using the global tool (w/o the compilation server).
• Can now set this to false to disable updates of the global h5 compiler.

If using the local compiler always set UpdateH5 to false - never update or install.

[mjrist]

@theolivenbaum any thoughts on this change? I'm open to suggestions. I've tested this out and it works great for us. We would love to see this merged in.