Swap two arguments to resolve bug
Swap two arguments to resolve bug

**Related issue**: N/A

**Type of change**: bug fix

**Impact**: other

**Release Notes**
The string of path for "-ip-vivado-tcls" could be empty ("")
For example, run "make SUB_PROJECT=arty bitstream" will get errors due the argument parsing in [prologue.tcl](https://github.com/sifive/fpga-shells/blob/d4b3878e4f5cf5c4621dbfe9b0bda1ed0dd3b995/xilinx/common/tcl/prologue.tcl)
Swaping the two arguments can resolve bug.
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