[clang] [AArch64][RISCV] Document option --print-supported-extensions (PR #98698)

[Jonathan Thackray via cfe-commits]

https://github.com/jthackray created https://github.com/llvm/llvm-project/pull/98698

Add documentation for the `--print-supported-extensions`
option which appears to be missing at present.

>From 8071d6f5da6d6a236a558e1488f2d9f1eb51719b Mon Sep 17 00:00:00 2001
From: Jonathan Thackray <jonathan.thackray at arm.com>
Date: Fri, 12 Jul 2024 23:08:28 +0100
Subject: [PATCH] [AArch64][RISCV] Document option --print-supported-extensions

Change-Id: Ib0ff5deeb9415818ccd0480cfbcdadc97ddc9872
---
 clang/docs/CommandGuide/clang.rst | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/clang/docs/CommandGuide/clang.rst b/clang/docs/CommandGuide/clang.rst
index a348f3640c5e..2def6ab41c70 100644
--- a/clang/docs/CommandGuide/clang.rst
+++ b/clang/docs/CommandGuide/clang.rst
@@ -400,6 +400,14 @@ number of cross compilers, or may only support a native target.
   option is only supported on AArch64 and RISC-V. On RISC-V, this option also
   prints out the ISA string of enabled extensions.
 
+.. option:: --print-supported-extensions
+
+  Prints the list of extensions that are supported for any possible CPU target
+  for the architecture specified by the combination of `--target`, `-march`,
+  and `-mcpu` values. Currently, this option is only supported on AArch64
+  and RISC-V. On RISC-V, this option also prints out the ISA string of
+  enabled extensions.
+
 Code Generation Options
 ~~~~~~~~~~~~~~~~~~~~~~~