Just to close this issue, I figure out the problem.
I added the following constraint to set the pin in the carrier board.
set_property PACKAGE_PIN C22 [get_ports
gpio_rtl]
set_property IOSTANDARD LVCMOS33 [get_ports
gpio_rtl]
And Vivado gave this error.
[DRC NSTD-1] Unspecified I/O Standard: 1 out of 138 logical ports use I/O standard (IOSTANDARD) value 'DEFAULT', instead of a user assigned specific value. This may cause I/O contention or incompatibility with the board power or connectivity affecting performance, signal integrity or in extreme cases cause damage to the device or the components to which it is connected. To correct this violation, specify all I/O standards. This design will fail to generate a bitstream unless all logical ports have a user specified I/O standard value defined. To allow bitstream creation with unspecified I/O standard values (not recommended), use this command: set_property SEVERITY {Warning} [get_drc_checks NSTD-1]. NOTE: When using the Vivado Runs infrastructure (e.g. launch_runs Tcl command), add this command to a .tcl file and add that file as a pre-hook for write_bitstream step for the implementation run. Problem ports:
gpio_rtl_tri_o[0].
However, if you pay attention to the parts in bold, you will see that its only a matter of incorrect pin name in the constraint file. Once I corrected it as follows, it worked
set_property PACKAGE_PIN C22 [get_ports
gpio_rtl_tri_o[0]]
set_property IOSTANDARD LVCMOS33 [get_ports
gpio_rtl_tri_o[0]]
Thanks to Xilinx to the wonderful and insightful error message that leads to nowhere !!!!

regards,
Alexandre Amory