arm: Update README.arm.md with Crouton instructions

README.arm.md

@@ -1,23 +1,33 @@
-Compiling on ARM
-----------------
+# Building Julia on ARM
 
-Julia has been compiled on several ARMv7 / Cortex A15 Samsung Chromebooks running
-Ubuntu Linux. This is a work in progress: several tests are known to fail, and
-backtraces are not available.
+Julia has been compiled on several ARMv7 / Cortex A15 Samsung
+Chromebooks running Ubuntu Linux under Crouton. This is a work in
+progress - several tests are known to fail, and backtraces are not
+available.
 
-Please start from the standard [build instructions](README.md#source-download-and-compilation),
-in particular the Linux notes.
-
-In addition to the standard `build-essentials` toolchain the following libraries
-must be installed to build on ARM:
+In addition to the standard `build-essentials` toolchain the following
+libraries must be installed to build on ARM:
 
 - libblas3gf, liblapack3gf, libfftw3-dev, libgmp3-dev, libmpfr-dev
 
-Next, create a file in the `julia` directory called `Make.user` with the
-following contents:
+Please start from the standard [build
+instructions](README.md#source-download-and-compilation), in
+particular the Linux notes.
+
+Next, create a file in the `julia` top-level directory called
+`Make.user` with the following contents:
 
 ```
 include $(JULIAHOME)/ARM.inc
 ```
 
-Then proceed to build as described in the primary README.
+Then proceed to build as described in the primary README. Just typing
+`make -j 4` at this stage should build julia.
+
+# Installing Crouton for Chromebooks
+
+If you do not have an Ubuntu chroot running on your Chromebook using
+Crouton, you can do so by following these tutorials.
+
+- [Crouton Tutorial 1](http:https://www.howtogeek.com/162120/how-to-install-ubuntu-linux-on-your-chromebook-with-crouton/)
+- [Crouton Tutorial 2](http:https://lifehacker.com/how-to-install-linux-on-a-chromebook-and-unlock-its-ful-509039343)