OK it seems something works

I copied KinetisSDHC.c , Sd2Card.h from Pauls Teensy library
Changed -pins_TEENSY35_36.h - SDSS to BUILTIN_SDCARD
-Sd2Card.h - #include "src/HAL/HAL_TEENSY35_36/spi_pins.h"
Commented out Sd2Card.h lines: -uint8_t const SPI_FULL_SPEED = 0;
-uint8_t const SPI_FULL_SPEED = 1;
-uint8_t const SPI_FULL_SPEED = 2;
-uint8_t const SD_CHIP_SELECT_PIN = SS_PIN;
-uint8_t const SPI_MOSI_PIN = MOSI_PIN;
-uint8_t const SPI_MISO_PIN = MISO_PIN;
-uint8_t const SPI_SCK_PIN = SCK_PIN;
Hope I'm not forgeting anything (I tried multiple variants).
I don't know if this is the right thing to do or if I broke any parts of the code. But with these modifications the code compiles and I can init the card and read contents of the card and see the filenames

Update: it seems to work. The files are beeing read, in repetier you can upload files, mounting and dismounting works
