Document the C compiler requirement

Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
diff --git a/scripts/make_generated_files.bat b/scripts/make_generated_files.bat
index f9c3c74..3d5f32d 100644
--- a/scripts/make_generated_files.bat
+++ b/scripts/make_generated_files.bat
@@ -3,6 +3,8 @@
 @rem Requirements:

 @rem * Perl must be on the PATH ("perl" command).

 @rem * Python 3.8 or above must be on the PATH ("python" command).

+@rem * Either a C compiler called "cc" must be on the PATH, or

+@rem   the "CC" environment variable must point to a C compiler.

 

 @rem @@@@ library\** @@@@

 @rem psa_crypto_driver_wrappers.h needs to be generated prior to