build: Fix cmake warning

Fix the following CMake warning in recent versions:

"CMake Warning (dev) at CMakeLists.txt:231 (FIND_PACKAGE):
 Policy CMP0148 is not set: The FindPythonInterp and FindPythonLibs modules
 are removed.  Run "cmake --help-policy CMP0148" for policy details.  Use
 the cmake_policy command to set the policy and suppress this warning.

 This warning is for project developers.  Use -Wno-dev to suppress it."

Signed-off-by: Edward Srouji <[email protected]>

CMakeLists.txt

@@ -214,19 +214,27 @@ if (NOT HAVE_WORKING_WERROR)
  message(FATAL_ERROR "-Werror doesn't work (compiler always creates warnings?). Werror is required for CMake.")
 endif()
 
-# Look for Python. We prefer some variant of python 3 if the system has it.
-FIND_PACKAGE(PythonInterp 3 QUIET)
-if (PythonInterp_FOUND)
- # pyverbs can only use python3:
- if (NO_PYVERBS)
- set(CYTHON_EXECUTABLE "")
+# Use Python modules based on CMake version for backward compatibility
+set(CYTHON_EXECUTABLE "")
+if (${CMAKE_VERSION} VERSION_LESS "3.12")
+ # Look for Python. We prefer some variant of python 3 if the system has it
+ FIND_PACKAGE(PythonInterp 3 QUIET)
+ if (PythonInterp_FOUND)
+ # pyverbs can only use python3:
+ if (NOT NO_PYVERBS)
+ FIND_PACKAGE(cython)
+ endif()
  else()
- FIND_PACKAGE(cython)
+ # But we still must have python (be it 2) for the build process
+ FIND_PACKAGE(PythonInterp REQUIRED)
  endif()
 else()
- # But we still must have python (be it 2) for the build process:
- FIND_PACKAGE(PythonInterp REQUIRED)
- set(CYTHON_EXECUTABLE "")
+ # FindPython looks preferably for Python3. If not found, version 2 is searched
+ FIND_PACKAGE(Python COMPONENTS Interpreter REQUIRED)
+ set(PYTHON_EXECUTABLE ${Python_EXECUTABLE})
+ if (NOT NO_PYVERBS AND Python_VERSION_MAJOR EQUAL 3)
+ FIND_PACKAGE(cython)
+ endif()
 endif()
 
 find_program(SYSTEMCTL_BIN systemctl HINTS "/usr/bin" "/bin")
@@ -450,8 +458,15 @@ if (CYTHON_EXECUTABLE)
  # find a matching -devel installation but will happily return a non-matching
  # one too. We need them both to match exactly to guarantee cython does the
  # right thing.
- FIND_PACKAGE(PythonLibs ${PYTHON_VERSION_MAJOR}.${PYTHON_VERSION_MINOR}
- EXACT REQUIRED)
+ if (${CMAKE_VERSION} VERSION_LESS "3.12")
+ FIND_PACKAGE(PythonLibs ${PYTHON_VERSION_MAJOR}.${PYTHON_VERSION_MINOR}
+ EXACT REQUIRED)
+ else()
+ FIND_PACKAGE(Python ${Python_VERSION_MAJOR}.${Python_VERSION_MINOR}
+ EXACT COMPONENTS Development REQUIRED)
+ set(PYTHON_LIBRARIES ${Python_LIBRARIES})
+ set(PYTHON_INCLUDE_DIRS ${Python_INCLUDE_DIRS})
+ endif()
 
  # Get a default installation path
  execute_process(COMMAND "${PYTHON_EXECUTABLE}" -c