Revise fake bool build advice from f789f6a.

The suggestions from that Craig Berry fellow were only half-baked.

pod/perlhacktips.pod

@@ -1338,8 +1338,12 @@ be truncated.  The C<cBOOL> macro exists to cast it correctly.
 On those platforms and compilers where C<bool> really is a boolean (C++,
 C99), it is easy to forget the cast.  You can force C<bool> to be a C<char>
 by compiling with C<-Accflags=-DPERL_BOOL_AS_CHAR>.  You may also wish to
-add C<-Accflags=-Werror=conversion> or your compiler's equivalent to make
-it impossible to ignore the unsafe truncations.
+run C<Configure> with something like
+
+     C<-Accflags='-Wconversion -Wno-sign-conversion -Wno-shorten-64-to-32'> 
+
+or your compiler's equivalent to make it easier to spot any unsafe truncations
+that show up.
 
 =head2 The .i Targets