Document the CMake generated files capability

Add a line in the README explaining that CMake will generate
the files it needs automatically on non-Windows systems
when not cross-compiling.

Signed-off-by: David Horstmann <david.horstmann@arm.com>
diff --git a/README.md b/README.md
index dbe6a23..e6924cb 100644
--- a/README.md
+++ b/README.md
@@ -67,6 +67,7 @@
 Any of the following methods are available to generate the configuration-independent files:
 
 * If not cross-compiling, running `make` with any target, or just `make`, will automatically generate required files.
+* On non-Windows systems, when not cross-compiling, CMake will generate the required files automatically.
 * Run `make generated_files` to generate all the configuration-independent files.
 * On Unix/POSIX systems, run `tests/scripts/check-generated-files.sh -u` to generate all the configuration-independent files.
 * On Windows, run `scripts\make_generated_files.bat` to generate all the configuration-independent files.