message: Fix "undefined reference to ..sqrt.." on HIP-clang
  It seems that HIP-clang doesn't calculate `sqrt(2)` in compile-time
  because of __device__ sqrt(enable_if<int>) overload in HIP
  causing this linking error:
  test_scan_by_key.cpp:(.text.startup+0x31): undefined reference to
  `_ZL4sqrtIiEN15__hip_enable_ifIXsr3std14numeric_limitsIT_EE10is_integerEdE4typeES1_'.
diff: @@ -23,7 +23,7 @@ POSSIBILITY OF SUCH DAMAGE.
  /* sqrt(2pi) */
  static double s2pi = 2.50662827463100050242E0;
  -static const double one_o_sqrt2 = (1/sqrt(2));
  +static const double one_o_sqrt2 = (1/sqrt(2.0));
  /* approximation for 0 <= |y - 0.5| <= 3/8 */
  static double P0[5] = {
  