SDL_mixer: cmake: fix typo in PROJECT_SOURCE_DIR

SDL Commits
#1 
From 8c6c095c0800055a8eb88d43d8201a197dafabf0 Mon Sep 17 00:00:00 2001
From: Anonymous Maarten <[EMAIL REDACTED]>
Date: Sat, 23 Jul 2022 17:04:21 +0200
Subject: [PATCH] cmake: fix typo in PROJECT_SOURCE_DIR

---
 CMakeLists.txt | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/CMakeLists.txt b/CMakeLists.txt
index a12b0caa..810e1856 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -25,7 +25,7 @@ project(SDL2_mixer
 
 message(STATUS "Configuring ${PROJECT_NAME} ${PROJECT_VERSION}")
 
-if(CMAKE_SOURCE_DIR STREQUAL PROJET_SOURCE_DIR)
+if(CMAKE_SOURCE_DIR STREQUAL PROJECT_SOURCE_DIR)
     set(SDL2MIXER_ROOTPROJECT ON)
 else()
     set(SDL2MIXER_ROOTPROJECT OFF)