diff --git a/contrib/jenkins_common.sh b/contrib/jenkins_common.sh
index e52a96a..6cfa334 100644
--- a/contrib/jenkins_common.sh
+++ b/contrib/jenkins_common.sh
@@ -4,4 +4,20 @@
 
 verify_value_string_arrays_are_terminated.py $(find . -name "*.[hc]")
 
-autoreconf --install --force
+prep_build() {
+    _src_dir="$1"
+    _build_dir="$2"
+
+    cd "$_src_dir"
+
+    # a failed 'make distcheck' may leave files without write permissions
+    chmod -R a+w .
+    git clean -dxf
+    # make absolutely sure no src files have modifications
+    git checkout -f HEAD
+
+    autoreconf --install --force
+
+    mkdir -p "$_build_dir"
+    cd "$_build_dir"
+}