bpo-41721: Add xlc options (GH-22097)

(cherry picked from commit 84a7917)

Authored-by: Stefan Krah <skrah@bytereef.org>

Author: miss-islington

configure

@@ -7588,11 +7588,14 @@ $as_echo "$MACOSX_DEPLOYMENT_TARGET" >&6; }
     ;;
 esac
 
-# ICC needs -fp-model strict or floats behave badly
 case "$CC" in
 *icc*)
+    # ICC needs -fp-model strict or floats behave badly
     CFLAGS_NODIST="$CFLAGS_NODIST -fp-model strict"
     ;;
+*xlc*)
+    CFLAGS_NODIST="$CFLAGS_NODIST -qalias=noansi -qmaxmem=-1"
+    ;;
 esac
 
 if test "$assertions" = 'true'; then

configure.ac

@@ -1993,11 +1993,14 @@ yes)
     ;;
 esac
 
-# ICC needs -fp-model strict or floats behave badly
 case "$CC" in
 *icc*)
+    # ICC needs -fp-model strict or floats behave badly
     CFLAGS_NODIST="$CFLAGS_NODIST -fp-model strict"
     ;;
+*xlc*)
+    CFLAGS_NODIST="$CFLAGS_NODIST -qalias=noansi -qmaxmem=-1"
+    ;;
 esac
 
 if test "$assertions" = 'true'; then