Toolchain.  I run on linux, these examples are tested on linux, other
than subtle differences like rm vs del in the Makefile, you should be
able to use these examples on a windows or mac system.

My code is written to be somewhat generic, but the assembly and in
particular the linker script are specific to the gnu tools because
that is how the toolchain world works unfortunately.  Since everyone
can get the gnu tools, they are available for Windows, Mac and Linux,
but not everyone can or wants to use the pay-for tools (or free tools
that are specific to one operating system) these examples are written
and tested using a gnu tool chain.  My personal style is such that
this code tends to port across the various versions of the gnu tools
also it is not specific to arm-none-eabi, arm-none-gnueabi,
arm-linux-gnueabi and so on.  You may need to change the ARMGNU line
at the top of my Makefile though.

So, if you are running Ubuntu Linux or a derivative you might only
need to do this:

apt-get install gcc-arm-linux-gnueabi binutils-arm-linux-gnueabi

Or you can go here and get a pre-built for your operating system

https://launchpad.net/gcc-arm-embedded

Or in another one of my github repositories you can get a build_arm
script

https://github.com/dwelch67/build_gcc

Which builds a cross compiler from sources.  Here again tested on
Linux (Ubuntu derivative) I used to use prior versions of this
script on Windows, but I gave up on maintaining that...This latter
build from the script is what I use as my daily driver arm toolchain.

Easier to come by but you can also get the llvm/clang toolchain as
an alternate compiler, it is not like gcc, one toolchain supports
all targets (normally).  I still use gnu binutils to do the assembling
and linking when using clang/llvm as a compiler (that part is target
specific for llvm).  So for this last solution you still need binutils
(which is easier to get built and working than gcc).  And my build_gcc
repo has a build_llvm script that I use for clang/llvm.