API to read the internal temperature sensor?

[torntrousers]

Is there any way to read the ESP32's internal temperature sensor from an Arduino sketch?

There's this IDF issue that mentions temprature_sens_read(), and from grep'ing I see that is in the Arduino code in esp32/tools/sdk/lib/librtc.a and /esp32/tools/sdk/lib/libesp32.a.

How can I call that?

[me-no-dev]

if there is no header defining the method, you are on your own :)
it's probably untested, unfinished or something else