diff --git a/src/script/lib-build.sh b/src/script/lib-build.sh
index a6ff447c99ee4..17c2fe72148c7 100644
--- a/src/script/lib-build.sh
+++ b/src/script/lib-build.sh
@@ -31,3 +31,20 @@ function ci_debug() {
         echo "CI_DEBUG: $*"
     fi
 }
+
+# get_processors returns 1/2 the value of the value returned by
+# the nproc program OR the value of the environment variable NPROC
+# allowing the user to tune the number of cores visible to the
+# build scripts.
+function get_processors() {
+    # get_processors() depends on coreutils nproc.
+    if [ -n "$NPROC" ]; then
+        echo "$NPROC"
+    else
+        if [ "$(nproc)" -ge 2 ]; then
+            echo "$(($(nproc) / 2))"
+        else
+            echo 1
+        fi
+    fi
+}
diff --git a/src/script/run-make.sh b/src/script/run-make.sh
index 3ab00861519d9..4331e581aa584 100755
--- a/src/script/run-make.sh
+++ b/src/script/run-make.sh
@@ -27,19 +27,6 @@ function clean_up_after_myself() {
     restore_ccache_conf
 }
 
-function get_processors() {
-    # get_processors() depends on coreutils nproc.
-    if test -n "$NPROC" ; then
-        echo $NPROC
-    else
-        if test $(nproc) -ge 2 ; then
-            expr $(nproc) / 2
-        else
-            echo 1
-        fi
-    fi
-}
-
 function detect_ceph_dev_pkgs() {
     local cmake_opts="-DWITH_FMT_VERSION=9.0.0"
     local boost_root=/opt/ceph