Increase CMake minimum version, move requirement (#422)

This is a very minor 'quality of life' improvement to `linesplitter` as
`cmake` nags about the minimum requirement being after (rather than
before) the main project declaration, and increasing the version (which
I understand you may not want to increase by as much) silences the
TIMESTAMP nag. Feel free to adjust or ignore, I just liked the quieter
build.

Author: eddelbuettel

examples/linesplitter/CMakeLists.txt

@@ -15,11 +15,17 @@
 # specific language governing permissions and limitations
 # under the License.
 
-project(linesplitter)
 cmake_minimum_required(VERSION 3.14)
+project(linesplitter)
 
 set(CMAKE_CXX_STANDARD 11)
 
+# Avoids a warning about timestamps on downloaded files (prefer new policy
+# if available))
+if(${CMAKE_VERSION} VERSION_GREATER_EQUAL "3.23")
+  cmake_policy(SET CMP0135 NEW)
+endif()
+
 include(FetchContent)
 
 fetchcontent_declare(nanoarrow