Skip the pip/wheel/auditwheel configure check.

PyDependences.cmake hard-fails configure if pip / wheel (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.

verified 2026-05-14 against bornagain-23.0.

--- a/cmake/multipython/PyDependences.cmake
+++ b/cmake/multipython/PyDependences.cmake
@@ -13,14 +13,10 @@
 # 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")
-    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 / 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 here keeps BA_PY_PACK=ON usable without a wheel toolchain.

 if (BA_TESTS)
     # Python packages needed for tests