ci/build.sh: CMake: use fallback for unset CMAKE_OPTIONS

This is no functional change but will allow treating unset variables
as errors in an upcoming commit.

diff --git a/ci/build.sh b/ci/build.sh
index 72dc530fb3d641f5a3e28e9fb3894eae65e0af3d..766785ac729f98cc70f7e381b4506c30a9a076f7 100755 (executable)
--- a/ci/build.sh
+++ b/ci/build.sh
@@ -23,7 +23,7 @@ build_system=${build_system:-autotools}
 if [ "${build_system}" = "cmake" ]; then
     mkdir build
     cd build
-    cmake ${CMAKE_OPTIONS} ..
+    cmake ${CMAKE_OPTIONS:-} ..
     cmake --build .
     cpack
     cd ..