pythongh-112970: Wire up closefrom for Linux

glibc-2.34 implements closefrom(3) using the same semantics as on BSD. Check
for closefrom in configure and use the check result in fileutils.c rather than
hardcoding a FreeBSD check (which was wrong for other BSDs anyway).

Signed-off-by: Sam James <sam@gentoo.org>

Python/fileutils.c

@@ -2878,9 +2878,9 @@ _Py_GetLocaleconvNumeric(struct lconv *lc,
  *    non-opened fd in the middle.
  * 2b. If fdwalk(3) isn't available, just do a plain close(2) loop.
  */
-#ifdef __FreeBSD__
+#ifdef HAVE_CLOSEFROM
 #  define USE_CLOSEFROM
-#endif /* __FreeBSD__ */
+#endif /* HAVE_CLOSEFROM */
 
 #ifdef HAVE_FDWALK
 #  define USE_FDWALK

configure.ac

@@ -4743,7 +4743,7 @@ fi
 
 # checks for library functions
 AC_CHECK_FUNCS([ \
-  accept4 alarm bind_textdomain_codeset chmod chown clock close_range confstr \
+  accept4 alarm bind_textdomain_codeset chmod chown clock closefrom close_range confstr \
   copy_file_range ctermid dup dup3 execv explicit_bzero explicit_memset \
   faccessat fchmod fchmodat fchown fchownat fdopendir fdwalk fexecve \
   fork fork1 fpathconf fstatat ftime ftruncate futimens futimes futimesat \