Add pipe backend symlink

diff --git a/regression-tests/modules/libpipebackend.so b/regression-tests/modules/libpipebackend.so
new file mode 120000 (symlink)
index 0000000..7eb1201
--- /dev/null
+++ b/regression-tests/modules/libpipebackend.so
@@ -0,0 +1 @@
+../../modules/pipebackend/.libs/libpipebackend.so
\ No newline at end of file