cmake/modules: always use the python3 specified in command line

if another python3 with higher version is found by
find_package(Python3), the cmake's install script would just
install the python modules/extensions into that python3's
dist-package directory, and the packaging script would fail
to find these artifacts when trying to package them.

so we need to ensure that the install directories for python
modeules/extensions are always "versioned" with WITH_PYTHON3
cmake option.

Signed-off-by: Kefu Chai <tchaikov@gmail.com>

diff --git a/cmake/modules/Distutils.cmake b/cmake/modules/Distutils.cmake
index 1d954c3a51f493cb93a802b781a0c3b4efdada60..d3aff02cd51c950e230767696dc381b984fe46cf 100644 (file)
--- a/cmake/modules/Distutils.cmake
+++ b/cmake/modules/Distutils.cmake
@@ -1,5 +1,16 @@
 include(CMakeParseArguments)
 
+# ensure that we are using the exact python version specified by
+# 'WITH_PYTHON3', in case some included 3rd party libraries call
+# 'find_package(Python3 ...) without specifying the exact version number. if
+# the building host happens to have a higher version of python3, that version
+# would be picked up instead by find_package(Python3). and that is not want we
+# expect.
+find_package(Python3 ${WITH_PYTHON3}
+  QUIET
+  REQUIRED
+  COMPONENTS Interpreter)
+
 function(distutils_install_module name)
   set(py_srcs setup.py README.rst requirements.txt test-requirements.txt bin ${name})
   foreach(src ${py_srcs})