[SYNTHESIS] May remove xilinx primitive from general filelist？

Description

When I used syn step, I got this error

Error:  ../src/lowrisc_prim_xilinx_ram_1p_0/rtl/prim_xilinx_ram_1p.sv:48: The construct 'string' is not supported in synthesis. (VER-700)
Compiling source file ../src/lowrisc_prim_abstract_flop_en_0/prim_flop_en.sv
Error:  Cannot recover from previous errors. (VER-518)
*** Presto compilation terminated with 2 errors. ***

The solution is straightforward: remove all Xilinx prims from the filelist and use generic prims for synthesis. However, I have two questions out of curiosity:

1. How can I manually eliminate the dependency on Xilinx prims in the filelist generation step during synthesis?
2. Why are Xilinx prims added to the general dependencies when they are only used in implementations targeting Xilinx FPGAs? I don’t think they should be included even for simulation, and in fact, they are never actually used at all—the code never takes this branch.

Start by tracing the synthesis filelist generation that includes src/lowrisc_prim_xilinx_ram_1p_0/rtl/prim_xilinx_ram_1p.sv, then compare it with the generic primitives used by synthesis. Done means the synthesis filelist excludes Xilinx primitives, uses the generic alternatives, and no longer reports the unsupported string construct or compilation failure.