gh-125206: Correct detection of complex numbers support in libffi (#126104)

Author: skirpichev

Misc/NEWS.d/next/Library/2024-10-29-07-24-52.gh-issue-125322.sstOM-.rst

@@ -0,0 +1 @@
+Correct detection of complex numbers support in libffi.

configure

@@ -4090,8 +4090,10 @@ AS_VAR_IF([have_libffi], [yes], [
 # See https://github.com/python/cpython/issues/125206 for more details.
 #
 AC_CACHE_CHECK([libffi has complex type support], [ac_cv_ffi_complex_double_supported],
-[ac_save_cc="$CC"
-CC="$CC -lffi"
+[WITH_SAVE_ENV([
+ CPPFLAGS="$LIBFFI_CFLAGS $CPPFLAGS"
+ LDFLAGS="$LIBFFI_LIBS $LDFLAGS"
+ LIBS="$LIBFFI_LIBS $LIBS"
 AC_RUN_IFELSE([AC_LANG_SOURCE([[
 #include <complex.h>
 #include <ffi.h>
@@ -4118,7 +4120,7 @@ int main(void)
 ]])], [ac_cv_ffi_complex_double_supported=yes],
 [ac_cv_ffi_complex_double_supported=no],
 [ac_cv_ffi_complex_double_supported=no])
-CC="$ac_save_cc"])
+])])
 if test "$ac_cv_ffi_complex_double_supported" = "yes"; then
     AC_DEFINE([Py_FFI_SUPPORT_C_COMPLEX], [1],
               [Defined if _Complex C type can be used with libffi.])