Error in ./build.sh setp of rocket-tools

**Type of issue**: bug report

**Impact**: no functional change

I'm using fedora 39 and the actual commit hash is `ca6dc52742914ab5f9b7fd1444fa0ffbae9aa631

The problem is when I run `./build.sh` (i tried too `./build.sh --with-arch=rv64gc_zfencei `) , but still get the same error:

```
Installing project fsf-binutils-gdb
libtool: install: warning: remember to run `libtool --finish /nowhere'

Removing existing riscv-pk/build directory
Configuring project riscv-pk
Building project riscv-pk
../dummy_payload/dummy_entry.S: Assembler messages:
../dummy_payload/dummy_entry.S:23: Warning: unterminated string; newline inserted
../dummy_payload/dummy_entry.S:24: Warning: unterminated string; newline inserted
../dummy_payload/dummy_entry.S:25: Warning: unterminated string; newline inserted
../dummy_payload/dummy_entry.S:26: Warning: unterminated string; newline inserted
../dummy_payload/dummy_entry.S:27: Warning: unterminated string; newline inserted
../dummy_payload/dummy_entry.S:28: Warning: unterminated string; newline inserted
../dummy_payload/dummy_entry.S:29: Warning: unterminated string; newline inserted
~/Documentos/rocket-chip/rocket-tools/lib/gcc/riscv64-unknown-elf/12.2.0/../../../../riscv64-unknown-elf/bin/ld: warning: dummy_payload has a LOAD segment with RWX permissions
../machine/flush_icache.c: Assembler messages:
../machine/flush_icache.c:4: Error: unrecognized opcode `fence.i', extension `zifencei' required
gmake: *** [Makefile:336: flush_icache.o] Error 1
```

I can't found a solution for that in others issues.

Thanks!

Start by reproducing ./build.sh, including the reported --with-arch=rv64gc_zfencei option. Read machine/flush_icache.c, dummy_payload/dummy_entry.S, and the Makefile rule at line 336; done means the riscv-pk build completes without the fence.i opcode error.

Written by the indexing model from the issue text.