INSTALL.rst: Add preliminary meson build instruction
CSP v2 support the meson build system.  Add a few lines so that users
can discover it.
How to install LibCSP
=====================
-CSP uses the `waf` build system (http://code.google.com/p/waf/). In order to
-compile CSP, you first need to configure the toolchain, what operating system
-to compile for, the location of required libraries and whether to enable
-certain optional features.
+CSP supports two build systems, the meson build system (https://mesonbuild.com/)
+and the waf build system (https://waf.io/).
+
+Using meson
+-----------
+
+In order to compile CSP with `meson`, you run the following commands:
+
+.. code-block:: bash
+ meson setup builddir
+ cd builddir
+ ninja
+
+You can use `meson configure` to change the core options as well as compiler or
+project options.
+
+
+Using waf
+---------
+
+In order to compile CSP with `waf`, you first need to configure the toolchain,
+what operating system to compile for, the location of required libraries and
+whether to enable certain optional features.
To configure CSP to build with the AVR32 toolchain for FreeRTOS and output
the compiled libcsp.a and header files to the install directory, issue:
