compel: add riscv64 support

Co-authored-by: Yixue Zhao <felicitia2010@gmail.com>
Co-authored-by: stove <stove@rivosinc.com>
Signed-off-by: Haorong Lu <ancientmodern4@gmail.com>
---
- rebased
- added a membarrier() to syscall table (fix authored by Cryolitia PukNgae)
Signed-off-by: PukNgae Cryolitia <Cryolitia@gmail.com>
Signed-off-by: Alexander Mikhalitsyn <aleksandr.mikhalitsyn@canonical.com>

scripts/nmk/scripts/include.mk

@@ -21,6 +21,7 @@ ARCH	?= $(shell echo $(SUBARCH) | sed	\
                 -e s/mips.*/mips/		\
                 -e s/sh[234].*/sh/		\
                 -e s/aarch64.*/aarch64/		\
+                -e s/riscv64.*/riscv64/		\
                 -e s/loongarch64.*/loongarch64/)
 
 export SUBARCH ARCH