change hash_str creation to use snprintf

src/shader.cpp

@@ -43,10 +43,10 @@ addShaderProgram(MemoryArena* arena,
 	const char* name)
 {
 	LOGF(Info, "loading shader, %s\n", name);
-	// TODO: replace std::string w/ utilAllocCStr() ?
-	std::string hash_str = std::string(vs) + std::string(fs);
 	const u32 max_len = 256;
-	u64 hash = utilFNV64a_str(hash_str.substr(0, max_len).c_str());
+	char input_str[max_len];
+	snprintf(input_str, max_len, "%s%s", vs, fs);
+	u64 hash = utilFNV64a_str(input_str);
 
 	if (getShaderByHash(gl_ctx, hash)) {
 		LOGF(Error, "shader is already loaded\n");