build.sh: Stop thread allocation on dual-threaded devices

build.sh

@@ -61,9 +61,12 @@ build() {
             -DANDROID_STL=c++_static
     done
 
+    CORES=$(($(nproc --all) - 2))
+    [ $CORES -eq 0 ] && CORES=2
+
     for a in ${TARGET_ABI_LIST[@]}; do
-        echo "Building $a artifacts... Using $(($(nproc) - 2)) thread."
-        cmake --build build_$a -j$(($(nproc) - 2))
+        echo "Building $a artifacts... Using $CORES  thread."
+        cmake --build build_$a -j$CORES
         echo "$a build complete, artifacts: $PWD/build_$a"
     done
 }