setup.py: add swig verison to _build.py.

Author: julian-smith-artifex-com

setup.py

@@ -736,12 +736,27 @@ def add(flavour, from_, to_):
     except Exception as e:
         log(f'Failed to get git information: {e}')
         sha, comment, diff, branch = (None, None, None, None)
+    swig = PYMUPDF_SETUP_SWIG or 'swig'
+    swig_version_text = run(f'{swig} --version', capture=1)
+    m = re.search('\nSWIG Version ([^\n]+)', swig_version_text)
+    log(f'{swig_version_text=}')
+    assert m, f'Unrecognised {swig_version_text=}'
+    swig_version = m.group(1)
+    def int_or_0(text):
+        try:
+            return int(text)
+        except Exception:
+            return 0
+    swig_version_tuple = tuple(int_or_0(i) for i in swig_version.split('.'))
+    log(f'{swig_version=}')
     text = ''
     text += f'mupdf_location = {mupdf_location!r}\n'
     text += f'pymupdf_version = {version_p!r}\n'
     text += f'pymupdf_git_sha = {sha!r}\n'
     text += f'pymupdf_git_diff = {diff!r}\n'
     text += f'pymupdf_git_branch = {branch!r}\n'
+    text += f'swig_version = {swig_version!r}\n'
+    text += f'swig_version_tuple = {swig_version_tuple!r}\n'
     add('p', text.encode(), f'{to_dir}/_build.py')
 
     # Add single README file.