Return true in wxSetEnv for unsetenv case.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@47946 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/unix/utilsunx.cpp

@@ -1104,7 +1104,7 @@ static bool wxDoSetEnv(const wxString& variable, const char *value)
         // don't test unsetenv() return value: it's void on some systems (at
         // least Darwin)
         unsetenv(variable.mb_str());
-        return;
+        return true;
 #else
         value = ""; // we can't pass NULL to setenv()
 #endif