Adjust rules for enabling native execution

The original build system automatically uses qemu-arm to run the
compiler when targeting Arm32 if the native environment is not armv7l.

However, some machines with armv8 or newer architectures, such as
Raspberry Pi 3 through Raspberry Pi 5, are also capable of performing
native execution. Additionally, GitHub's Arm64 runners can also perform
as well.

Therefore, This commit updates the build system to detect the host
machine and enable native execution when it is supported.

Author: DrXiao

Makefile

@@ -36,10 +36,10 @@ STAGE0 := shecc
 STAGE1 := shecc-stage1.elf
 STAGE2 := shecc-stage2.elf
 
+USE_QEMU ?= 1
 OUT ?= out
 ARCHS = arm riscv
 ARCH ?= $(firstword $(ARCHS))
-HOST_ARCH = $(shell arch 2>/dev/null)
 SRCDIR := $(shell find src -type d)
 LIBDIR := $(shell find lib -type d)
 

mk/arm.mk

@@ -1,4 +1,10 @@
-ARCH_NAME = armv7l
+# Allow the following machines to use native execution
+#
+# - Beaglebone Black (Cortex-A8)
+# - Raspberry Pi 3 (Cortex-A53)
+# - Raspberry Pi 4 (Cortex-A72)
+# - Raspberry Pi 5 (Cortex-A76)
+ALLOW_MACHINES = BeagleBone-Black Raspberry-Pi-3 Raspberry-Pi-4 Raspberry-Pi-5
 ARCH_RUNNER = qemu-arm
 ARCH_DEFS = \
     "/* target: ARM */\n$\
@@ -14,6 +20,39 @@ ARCH_DEFS = \
     \#define MAX_ARGS_IN_REG 4\n$\
     "
 
+# If the running machine has the "fastfetch" tool installed, the build
+# system will verify whether native execution can be performed.
+ifneq ($(shell which fastfetch),)
+    # 1. Replace whitespaces with hyphens after retrieving the host
+    #    machine name via the "fastfetch" tool.
+    #
+    # 2. If at least one machine name in the allowlist is found in
+    #    the host machine name, it can perform native execution.
+    #
+    #    Therefore, set USE_QEMU to 0.
+    HOST_MACHINE = $(shell fastfetch --logo none --structure Host | sed 's/ /-/g')
+    USE_QEMU = $(if $(strip $(foreach MACHINE, $(ALLOW_MACHINES), $(findstring $(MACHINE),$(HOST_MACHINE)))),0,1)
+
+    # Special case: GitHub workflows on Arm64 runners
+    #
+    # When an Arm-hosted runner executes "fastfetch --logo none --structure Host",
+    # it produces the following output:
+    # 
+    #     Host: Virtual Machine (Hyper-V UEFI Release v4.1)
+    #
+    # Arm-hosted runners are also capable of performing native execution. However,
+    # directly adding "Virtual-Machine" to the allowlist would be ambiguous.
+    # Therefore, the build system instead checks the CPU name using the
+    # "fastfetch --logo none --structure CPU" command.
+    #
+    # If the detected CPU is "Neoverse-N2", the build system treats the running
+    # machine as an Arm-hosted runner and enable native execution.
+    ifeq ($(USE_QEMU),1)
+        HOST_CPU = $(shell fastfetch --logo none --structure CPU)
+        USE_QEMU = $(if $(strip $(findstring Neoverse-N2,$(HOST_CPU))),0,1)
+    endif
+endif
+
 # Find the sysroot of the ARM GNU toolchain if using dynamic linking.
 #
 # Since developers may install the toolchain manually instead of
@@ -23,7 +62,7 @@ ARCH_DEFS = \
 # Therefore, the following process first locates find the correct
 # sysroot of the toolchain, and then generate the ELF interpreter
 # prefix for later use.
-ifneq ($(HOST_ARCH),$(ARCH_NAME))
+ifeq ($(USE_QEMU),1)
     ifeq ($(DYNLINK),1)
         CROSS_COMPILE = arm-none-linux-gnueabihf-
         ARM_CC = $(CROSS_COMPILE)gcc

mk/common.mk

@@ -25,7 +25,7 @@ pass = $(PRINTF) "$(PASS_COLOR)$1 Passed$(NO_COLOR)\n"
 # Check the prerequisites
 PREREQ_LIST := dot jq
 TARGET_EXEC ?=
-ifneq ($(HOST_ARCH),$(ARCH_NAME))
+ifeq ($(USE_QEMU),1)
     # Add qemu to the list if the host and target architectures differ
     PREREQ_LIST += $(ARCH_RUNNER)
     ifeq ($(filter $(ARCH_RUNNER),$(notdir $(shell which $(ARCH_RUNNER)))),)

mk/riscv.mk

@@ -1,5 +1,5 @@
-# Enforce the use qemu of by setting the ARCH_NAME variable to empty
-ARCH_NAME =
+# Enforce the use qemu of by setting the ALLOW_MACHINES variable to empty
+ALLOW_MACHINES =
 ARCH_RUNNER = qemu-riscv32
 ARCH_DEFS = \
     "/* target: RISCV */\n$\