bpo-42604: always set EXT_SUFFIX=${SOABI}${SHLIB_SUFFIX} when using configure (GH-23708)

Now all platforms use a value for the "EXT_SUFFIX" build variable derived
from SOABI (for instance in FreeBSD, "EXT_SUFFIX" is now ".cpython-310d.so"
instead of ".so"). Previously only Linux, Mac and VxWorks were using a value
for "EXT_SUFFIX" that included "SOABI".

Co-authored-by: Pablo Galindo <pablogsal@gmail.com>
diff --git a/configure b/configure
index d9e610e..f07edff 100755
--- a/configure
+++ b/configure
@@ -15429,13 +15429,7 @@
 
 fi
 
-
-case $ac_sys_system in
-    Linux*|GNU*|Darwin|VxWorks)
-	EXT_SUFFIX=.${SOABI}${SHLIB_SUFFIX};;
-    *)
-	EXT_SUFFIX=${SHLIB_SUFFIX};;
-esac
+EXT_SUFFIX=.${SOABI}${SHLIB_SUFFIX}
 
 { $as_echo "$as_me:${as_lineno-$LINENO}: checking LDVERSION" >&5
 $as_echo_n "checking LDVERSION... " >&6; }