bpo-44394: Ensure libexpat is linked against libm (GH-28617)

(cherry picked from commit 6c1154b)

Co-authored-by: Pablo Galindo Salgado <[email protected]>

Author: miss-islington

setup.py

@@ -1686,7 +1686,9 @@ def detect_expat_elementtree(self):
                 ('XML_POOR_ENTROPY', '1'),
             ]
             extra_compile_args = []
-            expat_lib = []
+            # bpo-44394: libexpact uses isnan() of math.h and needs linkage
+            # against the libm
+            expat_lib = ['m']
             expat_sources = ['expat/xmlparse.c',
                              'expat/xmlrole.c',
                              'expat/xmltok.c']