SDL_mixer: FindOpus: only append /opus to include path when it actually exists

From a5f350f7b8e4818133c678b176ef8605b37f9b65 Mon Sep 17 00:00:00 2001
From: Anonymous Maarten <[EMAIL REDACTED]>
Date: Fri, 12 Jan 2024 21:51:29 +0100
Subject: [PATCH] FindOpus: only append /opus to include path when it actually
 exists

---
 cmake/FindOpus.cmake | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/cmake/FindOpus.cmake b/cmake/FindOpus.cmake
index 030bb987..54562484 100644
--- a/cmake/FindOpus.cmake
+++ b/cmake/FindOpus.cmake
@@ -13,7 +13,9 @@ find_path(Opus_INCLUDE_PATH
     PATH_SUFFIXES opus
     HINTS ${PC_OPUS_INCLUDEDIR}
 )
-list(APPEND Opus_INCLUDE_PATH "${Opus_INCLUDE_PATH}/opus")
+if(EXISTS "${Opus_INCLUDE_PATH}/opus")
+    list(APPEND Opus_INCLUDE_PATH "${Opus_INCLUDE_PATH}/opus")
+endif()
 
 if(PC_OPUS_FOUND)
     get_flags_from_pkg_config("${Opus_LIBRARY}" "PC_OPUS" "_opus")