Move assemble soure files out off gnu folder

[xiaoxiang781216]

Summary

since all source files can be compiled with clang and armcc too.

• libc/machine/x86_64: Move all source files out of gnu folder
• libc/machine/riscv: Move all source files out of gnu folder
• libc/machine/renesas: Move all source files out of gnu folder
• libc/machine/arm64: Move all source files out of gnu folder
• libc/machine/arm: Move all source files out of gnu folder
• arch/arm: Move lib_dummy.c from arch/arm/src/common/ghs to libs/libc/machine/arm

Impact

Refine source code files layout

Testing

ci