[Info, not a issue] cmake settings for gcc version above v12

[cjacker]

1. Due to -march changes of gcc version above v12, to use gcc version above v12, RV_ARCH in cmake/application.cmake of hpm_sdk should be changed from -march=rv32imac to -march=rv32imac_zicsr_zifencei.

open cmake/application.cmake and find:

if(NOT RV_ARCH)
    set(RV_ARCH "rv32imac_zicsr_zifencei")
endif()

Change set(RV_ARCH "rv32imac") to set(RV_ARCH "rv32imac_zicsr_zifencei").

2. For users which use some prebuilt toolchains, such as xpack riscv toolchain, also need to set the gcc triplet in cmake/toolchain.cmake file to help SDK find the correct toolchain.

open cmake/toolchain.cmake and find:

elseif("${TOOLCHAIN_VARIANT}" STREQUAL "gcc")
  set(COMPILER gcc)
  set(LINKER ld)
  set(BINTOOLS gnu)
  set(C++ g++)
  set(CROSS_COMPILE_TARGET riscv32-unknown-elf)
  set(SYSROOT_TARGET       riscv32-unknown-elf)
  set(TOOLCHAIN_CMAKE gcc.cmake)

And change riscv32-unknown-elf to your toolchain's triplet, for example, for xpack riscv toolchain, it's riscv-none-elf.