Configurations/unix-Makefile.tmpl: don't leave empty .s files behind.

If pre-processor failed, an empty .s file could be left behind,
which could get successfully compiled if one simply re-ran make
and cause linking failures. Not anymore. Remove even intermediate .S
in case of pre-processor failure.
Reviewed-by: NRichard Levitte <levitte@openssl.org>

Configurations/unix-Makefile.tmpl

@@ -850,9 +850,9 @@ EOF
                    (my $target = $args{src}) =~ s|\.S$|.s|;
                    return <<"EOF";
 $target: $args{generator}->[0]
-	( trap "rm -f \$@.S" INT; \\
+	( trap "rm -f \$@.*" INT 0; \\
 	  $generator \$@.S; \\
-	  \$(CC) \$(CFLAGS) $incs -E -P \$@.S > \$@ && rm -f \$@.S )
+	  \$(CC) \$(CFLAGS) $incs -E -P \$@.S > \$@.i && mv -f \$@.i \$@ )
 EOF
               }
               # Otherwise....