Support to get nproc on macOS in the compilation (#8281)

Signed-off-by: Xiangyu Wang <xiangyu.wang@zilliz.com>

scripts/core_build.sh

@@ -2,7 +2,17 @@
 
 # Compile jobs variable; Usage: $ jobs=12 ./core_build.sh ...
 if [[ ! ${jobs+1} ]]; then
-    jobs=$(nproc)
+    if command -v nproc &> /dev/null
+    # For linux
+    then
+        jobs=$(nproc)
+    elif command -v sysctl &> /dev/null
+    # For macOS
+    then
+        jobs=$(sysctl -n hw.logicalcpu)
+    else
+        jobs=4
+    fi
 fi
 
 SOURCE="${BASH_SOURCE[0]}"