macOS Fix ofSystemLoadDialog objective-c++ (#8244)

Author: danoli3

libs/openFrameworksCompiled/project/osx/openFrameworksLib.xcodeproj/project.pbxproj

@@ -345,7 +345,7 @@
 		E4F3BAE612F4C745002D19BB /* ofLog.cpp */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.cpp; name = ofLog.cpp; path = ../../../openFrameworks/utils/ofLog.cpp; sourceTree = SOURCE_ROOT; };
 		E4F3BAE712F4C745002D19BB /* ofLog.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; name = ofLog.h; path = ../../../openFrameworks/utils/ofLog.h; sourceTree = SOURCE_ROOT; };
 		E4F3BAE812F4C745002D19BB /* ofNoise.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; name = ofNoise.h; path = ../../../openFrameworks/utils/ofNoise.h; sourceTree = SOURCE_ROOT; };
-		E4F3BAE912F4C745002D19BB /* ofSystemUtils.cpp */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.cpp; name = ofSystemUtils.cpp; path = ../../../openFrameworks/utils/ofSystemUtils.cpp; sourceTree = SOURCE_ROOT; };
+		E4F3BAE912F4C745002D19BB /* ofSystemUtils.cpp */ = {isa = PBXFileReference; explicitFileType = sourcecode.cpp.objcpp; fileEncoding = 4; name = ofSystemUtils.cpp; path = ../../../openFrameworks/utils/ofSystemUtils.cpp; sourceTree = SOURCE_ROOT; };
 		E4F3BAEA12F4C745002D19BB /* ofSystemUtils.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; name = ofSystemUtils.h; path = ../../../openFrameworks/utils/ofSystemUtils.h; sourceTree = SOURCE_ROOT; };
 		E4F3BAEB12F4C745002D19BB /* ofThread.cpp */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.cpp; name = ofThread.cpp; path = ../../../openFrameworks/utils/ofThread.cpp; sourceTree = SOURCE_ROOT; };
 		E4F3BAEC12F4C745002D19BB /* ofThread.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; name = ofThread.h; path = ../../../openFrameworks/utils/ofThread.h; sourceTree = SOURCE_ROOT; };