Set cmake min version to represent used features. (#2852)

# Checklist

- [x] The title and commit message(s) are descriptive.
- [x] Small commits made to fix your PR have been squashed to avoid
history pollution.
- [x] Tests have been added for new features or bug fixes.
- [x] API of new functions and classes are documented.

# Description
The cmake minimum required version was set to 3.29, which is newer than
what a lot of linux distros ship with, and was unnecessarily high for
the cmake features that were being used. This PR drops the min version
to 3.15 to reflect used features and improve out-of-the-box
compatibility.

Closes #2847.

Co-authored-by: Johan Mabille <[email protected]>

Author: ThisIsFineTM

CMakeLists.txt

@@ -7,7 +7,7 @@
 # The full license is in the file LICENSE, distributed with this software. #
 ############################################################################
 
-cmake_minimum_required(VERSION 3.22)
+cmake_minimum_required(VERSION 3.15..3.29)
 project(xtensor CXX)
 
 set(XTENSOR_INCLUDE_DIR ${CMAKE_CURRENT_SOURCE_DIR}/include)

test/CMakeLists.txt

@@ -7,7 +7,7 @@
 # The full license is in the file LICENSE, distributed with this software. #
 ############################################################################
 
-cmake_minimum_required(VERSION 3.29)
+cmake_minimum_required(VERSION 3.15..3.29)
 
 if (CMAKE_CURRENT_SOURCE_DIR STREQUAL CMAKE_SOURCE_DIR)
     project(xtensor-test CXX)