Skip the pip/wheel/auditwheel configure check.

PyDependences.cmake hard-fails configure if pip / wheel / setuptools (and
auditwheel on Linux) aren't importable, on the assumption that BA_PY_PACK=ON
means the user will run the ba_wheel target. Distro packaging keeps
BA_PY_PACK=ON to get the assembled ${CMAKE_BINARY_DIR}/py/src/bornagain/
tree (init + SWIG .py files + POST_BUILD-copied .so files) but never invokes
ba_wheel — the .py files get installed directly into Python site-packages
and the .so files are symlinked from /usr/lib64/. So the wheel-build tooling
check is gratuitous on Gentoo.

(24.0 added setuptools to the checked list; the check is otherwise the same
as 23.0.)

verified 2026-05-28 against bornagain-24.0.

--- a/cmake/multipython/PyDependences.cmake
+++ b/cmake/multipython/PyDependences.cmake
@@ -8,14 +8,11 @@
 # check presence of some Python modules
 message(STATUS "Searching required Python packages...")
 set(py_packages "")
-if (BA_PY_PACK)
-    # Python packages needed for building the BornAgain wheel
-    list(APPEND py_packages "pip;wheel;setuptools")
-    if(LINUX)
-        # on Linux, `auditwheel` is needed to produce 'manylinux' wheels repair (PEP 599)
-        list(APPEND py_packages "auditwheel")
-    endif()
-endif()
+# Wheel-build Python packages (pip / wheel / setuptools / auditwheel) are only
+# used by the ba_wheel custom target, which distro packagers don't invoke —
+# they consume the assembled ${CMAKE_BINARY_DIR}/py/src/bornagain/ tree
+# directly. Skipping the check keeps BA_PY_PACK=ON usable without a wheel
+# toolchain.

 if (BA_TESTS)
     # Python packages needed for tests