[3.10] bpo-44394: Ensure libexpat is linked against libm (GH-28617) (GH-28621)

* bpo-44394: Ensure libexpat is linked against libm (GH-28617)
(cherry picked from commit 6c1154b)

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

Author: 3 people

setup.py

@@ -1765,7 +1765,9 @@ def detect_expat_elementtree(self):
                 ('XML_POOR_ENTROPY', '1'),
             ]
             extra_compile_args = []
-            expat_lib = []
+            # bpo-44394: libexpat 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']