teensy36: add to smoketest

[aykevl]

This required some changes to the UART code to get it to compile on Go 1.11.

Smoke tests are very important to make sure -target=teensy36 doesn't break unexpectedly.

@ardnew can you take a look at these changes and test them on a Teensy 3.6? I don't have such a device.

[ardnew]

Code looks fine. I was able to rebuild tinygo (for the new -output flag), run make smoketest without any error at the new teensy36 target added. Was also able to flash examples/blinky1 to the device and it ran as expected.

However, I'm not getting any output on UART1 RX/TX (digital 0/1) when flashing examples/serial. I've tried both using -output=uart and not specifying the -output flag at all, and I've tried 2 different serial USB converters (CP2104 and MCP2221A).

Not sure if this was just introduced or if there was a problem before these changes. Will have to revert and test again.

[deadprogram]

@ardnew did you ever have a chance to test this again?

[ardnew]

@deadprogram i havent yet, no. As soon as i finish some stuff for actual work (this week) i will have a little free time to investigate

[deadprogram]

@ardnew can you please verify this, I want to merge.

@aykevl can you please resolve merge conflict?

Thank you!

[aykevl]

Rebased.

[aykevl]

Let's try that again. Now rebased on top of the (current) dev branch instead of an older version to fix the merge conflict.

[ardnew]

Looks like I introduced a bug from branch board/teensy40 with the build constraints in machine/uart.go, causing the CI checks to fail.

Build tag nxpmk66f18 doesn't exist. Should be nxp,mk66f18 or just mk66f18.

This will be fixed once branch feature/teensy40-uart gets merged, as it uses build tag nxp.

I think this precisely justifies adding teensy36 to smoketest!

With that bug fixed, I retested this (which depended on tinygo built from branch output-flag) by using -output=uart, and by not specifying flag -output at all, and I am successfully getting serial data from the examples/serial demo. So this should be good to go.

[deadprogram]

Now merging, thanks everyone!