SDL: Update README-riscos.md to reflect that atomic functions have been fixed

SDL Commits
1 
From 05e2c8f2ce020c9c891f21e245a6607360fe5c75 Mon Sep 17 00:00:00 2001
From: Cameron Cawley <[EMAIL REDACTED]>
Date: Tue, 22 Nov 2022 12:12:17 +0000
Subject: [PATCH] Update README-riscos.md to reflect that atomic functions have
 been fixed

---
 docs/README-riscos.md | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/docs/README-riscos.md b/docs/README-riscos.md
index f7ddb2e202a2..4c31b5cf7cf9 100644
--- a/docs/README-riscos.md
+++ b/docs/README-riscos.md
@@ -16,16 +16,18 @@ Currently, SDL for RISC OS only supports compiling with GCCSDK under Linux. Both
 
 The following commands can be used to build SDL for RISC OS using autoconf:
 
-    ./configure --host=arm-unknown-riscos --prefix=$GCCSDK_INSTALL_ENV --disable-gcc-atomics
+    ./configure --host=arm-unknown-riscos --prefix=$GCCSDK_INSTALL_ENV
     make
     make install
 
 The following commands can be used to build SDL for RISC OS using CMake:
 
-    cmake -Bbuild-riscos -DCMAKE_TOOLCHAIN_FILE=$GCCSDK_INSTALL_ENV/toolchain-riscos.cmake -DRISCOS=ON -DCMAKE_INSTALL_PREFIX=$GCCSDK_INSTALL_ENV -DCMAKE_BUILD_TYPE=Release -DSDL_GCC_ATOMICS=OFF
+    cmake -Bbuild-riscos -DCMAKE_TOOLCHAIN_FILE=$GCCSDK_INSTALL_ENV/toolchain-riscos.cmake -DRISCOS=ON -DCMAKE_INSTALL_PREFIX=$GCCSDK_INSTALL_ENV -DCMAKE_BUILD_TYPE=Release
     cmake --build build-riscos
     cmake --build build-riscos --target install
 
+When using GCCSDK 4.7.4 release 6 or earlier versions, the builtin atomic functions are broken, meaning it's currently necessary to compile with `--disable-gcc-atomics` using autotools or `-DSDL_GCC_ATOMICS=OFF` using CMake. Newer versions of GCCSDK don't have this problem.
+
 
 Current level of implementation
 -------------------------------
@@ -36,6 +38,4 @@ The filesystem APIs return either Unix-style paths or RISC OS-style paths based
 
 The audio, loadso, thread and timer APIs are currently provided by UnixLib.
 
-GCC atomics are currently broken on some platforms, meaning it's currently necessary to compile with `--disable-gcc-atomics` using autotools or `-DSDL_GCC_ATOMICS=OFF` using CMake.
-
 The joystick, locale and power APIs are not yet implemented.