fix: compilation issue for getting the process name (#163)

* fix: compilation issue for getting the process name

Resolves #162

src/datadog/platform_util.cpp

@@ -191,7 +191,7 @@ int get_process_id() {
 
 std::string get_process_name() {
 #if defined(__APPLE__) || defined(__FreeBSD__)
-  char* process_name = getprogname();
+  const char* process_name = getprogname();
   return (process_name != nullptr) ? process_name : "unknown-service";
 #elif defined(__linux__) || defined(__unix__)
   return program_invocation_short_name;