gsdx: add GStempdir wrapper to get a tempory directory

Allow to use Linux compatible code for OpenCL

plugins/GSdx/GSUtil.cpp

@@ -292,22 +292,13 @@ void GSUtil::GetDeviceDescs(list<OCLDeviceDesc>& dl)
 					desc.name = GetDeviceUniqueName(device);
 					desc.version = major * 100 + minor * 10;
 
-#ifdef _WIN32
+					desc.tmppath = GStempdir() + "/" + desc.name;
-					char* buff = new char[MAX_PATH + 1];
-					GetTempPath(MAX_PATH, buff);
-					desc.tmppath = string(buff) + "/" + desc.name;
 
 					GSmkdir(desc.tmppath.c_str());
 
-					sprintf(buff, "/%d", OCL_PROGRAM_VERSION);
+					desc.tmppath += "/" + std::to_string(OCL_PROGRAM_VERSION);
-					desc.tmppath += buff;
-					delete[] buff;
 
 					GSmkdir(desc.tmppath.c_str());
-#else
-					// TODO: linux
-					ASSERT(0);
-#endif
 
 					dl.push_back(desc);
 				}
@@ -455,6 +446,17 @@ void GSmkdir(const char* dir)
 #endif
 }
 
+std::string GStempdir()
+{
+#ifdef _WIN32
+	char path[MAX_PATH + 1];
+	GetTempPath(MAX_PATH, path);
+	return {path};
+#else
+	return "/tmp";
+#endif
+}
+
 const char* psm_str(int psm)
 {
 	switch(psm) {

plugins/GSdx/GSUtil.h

@@ -69,6 +69,7 @@ public:
 };
 
 void GSmkdir(const char* dir);
+std::string GStempdir();
 
 const char* psm_str(int psm);