Added crosstool and updated readme

.gitmodules

@@ -1,3 +1,6 @@
 [submodule "Dependencies/esp-idf"]
 	path = Dependencies/esp-idf
 	url = https://github.com/espressif/esp-idf
+[submodule "Dependencies/crosstool-NG"]
+	path = Dependencies/crosstool-NG
+	url = https://github.com/espressif/crosstool-NG.git

Dependencies/crosstool-NG

@@ -0,0 +1 @@
+Subproject commit 7c5693db97c8d87b4792958e6cffb16489ba7f26

ReadMe.org

@@ -1,3 +1,31 @@
 #+TITLE: esp32-timer
 
 A timing app designed to run on my Odroid-GO.
+
+* Setting up ESP-IDF
+[[https://docs.espressif.com/projects/esp-idf/en/latest/][See docs]].
+
+The following is to set up the toolchain by building as much of it from source as the docs have specified. While I could download a binary, I like the idea of compiling from source in case their website goes down. I'm doing this on Ubuntu 18.04.
+#+BEGIN_SRC sh
+# Dependencies
+sudo apt-get install git wget libncurses-dev flex bison gperf python python-pip python-setuptools python-serial python-click python-cryptography python-future python-pyparsing python-pyelftools cmake ninja-build ccache libffi-dev libssl-dev gawk gperf grep gettext python python-dev automake bison flex texinfo help2man libtool libtool-bin make
+
+# Submodules
+cd Dependencies/esp-idf/
+git submodule update --init
+
+# Crosstool - this builds GCC for ESP32. This will take a while (27 minutes in my case)
+cd ../crosstool-NG/
+git submodule update --init
+./bootstrap && ./configure --enable-local && make
+./ct-ng xtensa-esp32-elf
+./ct-ng build
+chmod -R u+w builds/xtensa-esp32-elf
+
+cd ../../
+mkdir -p tools
+IDF_TOOLS_PATH=$PWD/tools
+cd Dependencies/esp-idf/
+# TODO: This doesn't actually use the GCC I built, nor the tools path...
+./install.sh
+#+END_SRC