Fix audio

See merge request projectn/nexus-am!45

Jyy upstream

See merge request projectn/nexus-am!43

Audio

See merge request projectn/nexus-am!42

* this helps to avoid out-of-memory in fceux, since fceux will repeatly
  call malloc()/free() when copying data to the audio buffer

* this is to support 64-bit divisions in fceux

* ADDCYC() can still maintain soundtimestamp correctly

* this fixed the delay

* instead of waiting for a totally free buffer

* this can expose the status of the stream buffer to applications

am: add riscv64-sdi

See merge request projectn/nexus-am!41

add riscv32-noop

See merge request projectn/nexus-am!40

libs,klib,stdio: format 32-bit integer without 64-bit division

See merge request projectn/nexus-am!39

Update string.c : fix bug in strcat when dst start with '\0'

See merge request projectn/nexus-am!38

riscv64-nemu,cte: fix wrong store instruction in trap.S

See merge request projectn/nexus-am!37

am,sdi: use the rv64 engine in NEMU and add more isa

See merge request projectn/nexus-am!36

native,platform: use memfd_create() instead of shm_open()

am,arch,native: add rule for gdb

* memfd_create() is automatically released by the kernel, and it does
  not create any files on the filesystem

native,platform: fix wrong assert