Update samples README with macOS information (#226)

* Update samples README with macOS information

The LLVM Embedded Toolchain for Arm has a macOS release. Update
the samples README to claim support and to point the reader to
the instructions for installing QEMU.

macOS requires the developer tools to be installed to run the
samples, which also installs LLDB. The existing instructions
for Linux work for macOS.

* Update samples/README.md

Co-authored-by: Michael Platings <[email protected]>

* Update samples to note that we support four environments.

---------

Co-authored-by: Michael Platings <[email protected]>

Author: smithp35

samples/README.md

@@ -11,16 +11,17 @@ Embedded Toolchain for Arm.
 
 ## Supported environments
 
-The build scripts support three different environments:
+The build scripts support four different environments:
 * Linux
+* macOS
 * Windows
 * Windows + [MSYS2](https://www.msys2.org/)
 
 ## Prerequisites
 
 In order to compile the samples you will need the following tools:
 * LLVM Embedded Toolchain for Arm
-* GNU Make (Linux and MSYS2)
+* GNU Make (Linux, macOS and MSYS2)
 
 To run the samples you will need a QEMU emulator to be installed on your
 machine. The samples rely on
@@ -30,13 +31,17 @@ the QEMU Arm System emulator. On Ubuntu Linux it can be installed as follows:
 # apt-get install qemu-system-arm
 ```
 
+On macOS the QEMU Arm System emulator can be installed via HomeBrew or
+Mac Ports. Instructions can be found in
+https://www.qemu.org/download/#macos
+
 The Windows installer can be downloaded from
 https://www.qemu.org/download/#windows.
 
-To debug the samples you will need to install a debugger 
-that supports Arm targets, for example, 
+To debug the samples you will need to install a debugger
+that supports Arm targets, for example,
 [LLDB](https://lldb.llvm.org/) version matching LLVM Embedded Toolchain for Arm.
-Debugging is only supported on Linux.
+Debugging is only supported on Linux and macOS.
 
 ## Specifying the location of the installed toolchain
 
@@ -52,7 +57,7 @@ to the ``bin`` directory of the toolchain.
 
 ## Compiling, running and debugging the samples
 
-### Linux and MSYS2
+### Linux, macOS and MSYS2
 
 Change to the directory of a specific sample (e.g. ``src/baremetal-uart``) and
 use the following commands to build, run or debug the sample: