Enable installing xPack toolchain on macOS/arm64

Darwin and arm64 are used to identify the operating system and ISA of
Apple's dominant computer.

In addition, enhance shell compatibility by using $() instead of
backticks for command execution. Furthermore, abstract common variables
such as PARALLEL in .ci/common.sh.

Author: ChinYikMing

.ci/common.sh

@@ -1,15 +1,12 @@
-# Expect host is Linux/x86_64
+# Expect host is Linux/x86_64, Linux/aarch64, macOS/arm64
+
+MACHINE_TYPE=$(uname -m)
+OS_TYPE=$(uname -s)
+
 check_platform()
 {
-    MACHINE_TYPE=`uname -m`
-    OS_TYPE=`uname -s`
-
     case "${MACHINE_TYPE}/${OS_TYPE}" in
-        x86_64/Linux | aarch64/Linux)
-            ;;
-        Arm64/Darwin)
-            echo "Apple Silicon is not supported yet"
-            exit 1
+        x86_64/Linux | aarch64/Linux | arm64/Darwin)
             ;;
         *)
             echo "Unsupported platform: ${MACHINE_TYPE}/${OS_TYPE}"
@@ -18,3 +15,9 @@ check_platform()
     esac
 
 }
+
+if [[ "${OS_TYPE}" == "Linux" ]]; then
+  PARALLEL=-j$(nproc)
+else
+  PARALLEL=-j$(sysctl -n hw.logicalcpu)
+fi

.ci/riscv-tests.sh

@@ -1,15 +1,15 @@
 #!/usr/bin/env bash
 
+. .ci/common.sh
+
 set -e -u -o pipefail
 
 # Install RISCOF
 pip3 install git+https://github.com/riscv/riscof.git@d38859f85fe407bcacddd2efcd355ada4683aee4
 
 set -x
 
-export PATH=`pwd`/toolchain/bin:$PATH
-
-PARALLEL=-j$(nproc)
+export PATH=$(pwd)/toolchain/bin:$PATH
 
 make distclean
 # Rebuild with all RISC-V extensions

.ci/riscv-toolchain-install.sh

@@ -5,17 +5,20 @@ set -e -u -o pipefail
 . .ci/common.sh
 
 check_platform
-
 mkdir -p toolchain
 
 if [[ "$#" == "0" ]] || [[ "$1" != "riscv-collab" ]]; then
     GCC_VER=14.2.0-3
     TOOLCHAIN_REPO=https://github.com/xpack-dev-tools/riscv-none-elf-gcc-xpack
 
-    if [[ ${MACHINE_TYPE} == "x86_64" ]]; then
-        TOOLCHAIN_URL=${TOOLCHAIN_REPO}/releases/download/v${GCC_VER}/xpack-riscv-none-elf-gcc-${GCC_VER}-linux-x64.tar.gz
-    elif [[ ${MACHINE_TYPE} == "aarch64" ]]; then
-        TOOLCHAIN_URL=${TOOLCHAIN_REPO}/releases/download/v${GCC_VER}/xpack-riscv-none-elf-gcc-${GCC_VER}-linux-arm64.tar.gz
+    if [[ ${OS_TYPE} == "Linux" ]]; then
+        if [[ ${MACHINE_TYPE} == "x86_64" ]]; then
+            TOOLCHAIN_URL=${TOOLCHAIN_REPO}/releases/download/v${GCC_VER}/xpack-riscv-none-elf-gcc-${GCC_VER}-linux-x64.tar.gz
+        elif [[ ${MACHINE_TYPE} == "aarch64" ]]; then
+            TOOLCHAIN_URL=${TOOLCHAIN_REPO}/releases/download/v${GCC_VER}/xpack-riscv-none-elf-gcc-${GCC_VER}-linux-arm64.tar.gz
+        fi
+    else
+        TOOLCHAIN_URL=${TOOLCHAIN_REPO}/releases/download/v${GCC_VER}/xpack-riscv-none-elf-gcc-${GCC_VER}-darwin-arm64.tar.gz
     fi
 else
     UBUNTU_VER=`lsb_release -r | cut -f2`