build: make Python memory allocations valgrind friendly

When testing with

  meson test -C .build --wrap='valgrind --leak-check=full'

the Python binding will trigger 'Invalid read of size 4' warnings.
Tell Python to use malloc directly for all memory allocation which can
be properly traced by valgrind.

Signed-off-by: Daniel Wagner <dwagner@suse.de>

libnvme/meson.build

@@ -55,6 +55,7 @@ if have_python_support
     test_env = environment()
     test_env.append('MALLOC_PERTURB_', '0')
     test_env.append('PYTHONPATH', join_paths(meson.current_build_dir(), '..'))
+    test_env.append('PYTHONMALLOC', 'malloc')
 
     # Test section
     test('[Python] import libnvme', python3, args: ['-c', 'from libnvme import nvme'], env: test_env)