A string constant is, as the name says, a constant. So to make the warning go away, the proper solution would indeed be to turn the pointer into a const pointer.
If that cannot be done, you can explicit typecasts
ACE_TCHAR* argv[] = {const_cast<ACE_TCHAR*>("Input1"),
const_cast<ACE_TCHAR*>("Input2")};
or assign the strings to non-constant char arrays first
char input1[] = "Input1";
char input2[] = "Input2";
ACE_TCHAR* argv[] = {input1, input2};