Update documentation to reference binutils-gdb

Author: wnienhaus

README.rst

@@ -18,9 +18,10 @@ It can translate small assembly language programs to a loadable/executable
 ULP machine code binary, directly on the ESP32 microcontroller.
 
 This is intended as an alternative approach to assembling such programs using
-the binutils-esp32ulp toolchain from Espressif on a development machine.
+the `binutils-gdb toolchain <https://github.com/espressif/binutils-gdb/tree/esp32ulp-elf-2.35>`_
+(esp32-elf-as) from Espressif on a development machine.
 
-It can also be useful in cases where binutils-esp32ulp is not available.
+It can also be useful in cases where esp32-elf-as is not available.
 
 
 Features

docs/index.rst

@@ -151,7 +151,8 @@ Testing
 -------
 
 There are unit tests and also compatibility tests that check whether the binary
-output is identical with what binutils-esp32ulp produces.
+output is identical with what Espressif's esp32-elf-as (from their `binutils-gdb fork
+<https://github.com/espressif/binutils-gdb/tree/esp32ulp-elf-2.35>`_) produces.
 
 micropython-esp32-ulp has been tested on the Unix port of MicroPython and on real ESP32
 devices with the chip type ESP32D0WDQ6 (revision 1) without SPIRAM.