added script to compile esp32 xcompiler from scratch

esp32/scripts/install_esp32_xcompiler_scratch.sh

@@ -0,0 +1,38 @@
+#!/bin/bash
+
+# This script downloads the esp32 cross-compiler and compile it from scratch with crosstool-NG.
+# It doesn't install esp-idf tools.
+# Installation instructions from https://docs.espressif.com/projects/esp-idf/en/stable/get-started/linux-setup-scratch.html
+
+set -e
+
+SCRIPTDIR="$( cd "$( dirname "${BASH_SOURCE[0]}" )" >/dev/null 2>&1 && pwd )"   # dir from where this script is run
+CROSSTOOLNG_ESP_VERSION=2019r2
+
+### install some dependencies ###
+sudo apt-get install -y git wget libncurses-dev flex bison gperf python python-pip python-setuptools python-serial python-click python-cryptography python-future python-pyparsing python-pyelftools ninja-build ccache libffi-dev libssl-dev
+
+sudo apt-get install -y gawk gperf grep gettext python python-dev automake bison flex texinfo help2man libtool libtool-bin make git
+
+
+### Download and build cross-compilation toolchain ###
+if [ -z "$1" ]
+  then
+    INSTALLDIR = $DEFAULTINSTALLDIR
+else 
+     INSTALLDIR = $1
+fi
+
+mkdir -p $INSTALLDIR && cd $INSTALLDIR
+
+# download crosstool-NG and build it
+git clone https://github.com/espressif/crosstool-NG.git
+cd crosstool-NG
+git checkout esp-$CROSSTOOLNG_ESP_VERSION
+git submodule update --init
+./bootstrap && ./configure --enable-local && make -j8
+
+# build the toolchain (will be in esp/crosstool-NG/builds/xtensa-esp32-elf)
+./ct-ng xtensa-esp32-elf
+./ct-ng build
+chmod -R u+w builds/xtensa-esp32-elf