Error building rocket-tools on Ubuntu 20.04

[bbdd]

Building rocket-tools on Ubuntu 20.04 with this error:

$ export MAKEFLAGS=" -j20"
$ ./build.sh
...
../machine/flush_icache.c: Assembler messages:
../machine/flush_icache.c:4: Error: unrecognized opcode `fence.i', extension `zifencei' required
make: *** [Makefile:336: flush_icache.o] Error 1
make: *** Waiting for unfinished jobs....
../machine/mentry.S: Assembler messages:
../machine/mentry.S:93: Error: unrecognized opcode `fence.i', extension `zifencei' required
make: *** [Makefile:336: mentry.o] Error 1

It seems that I need to add zifencei extension. How to fix this error?

[Junxian Li]

This might help：
#17 (comment)

[bbdd]

This might help： #17 (comment)

Thanks. Adding --with-arch=rv64gc_zifencei in the build.sh script works.