Build: Add zicsr extension to all cpu when compiled with nuclei_llvm

Signed-off-by: Huaqi Fang <[email protected]>

Build/toolchain/nuclei_llvm.mk

@@ -93,6 +93,8 @@ endif
 COMMON_FLAGS += -march=$(RISCV_ARCH) -mabi=$(RISCV_ABI) -mcmodel=$(RISCV_CMODEL)
 # Enable some experimental extension for llvm clang
 COMMON_FLAGS += -menable-experimental-extensions
+# Add zicsr extension to clang, since our cpu always has zicsr extension
+COMMON_FLAGS += -Xclang -target-feature -Xclang +zicsr
 ## Append mtune options when RISCV_TUNE is defined
 ## It might be defined in SoC/<SOC>/build.mk, and can be overwritten by make
 ifneq ($(RISCV_TUNE),)