re: make rules when creating multiple files

[matthew green <mrg%eterna.com.au@localhost>]

> Matthew Green provided the following analysis for PR 45126 (parallel
> build breakage in Kerberos):
> 
> ----- Forwarded message from matthew green <mrg%eterna.com.au@localhost> -----
> 
> i think i may have figured out the cause of this.  i noticed that
> my build tree had hdb_asn1.h as a zero length file.  after a little
> bit of red-herring with seeing a similar zero length file in the
> src/compat build, i come across the rules in
> src/crypto/external/bsd/heimdal/Makefile.rules.inc:
> 
> ${ASN1_FILES.${src}} ${src:.asn1=_asn1.hx} ${src:.asn1=_asn1-priv.hx}: ${src} 
> \
>                                         ${src:.asn1=.opt} ${TOOL_ASN1_COMPILE}
>         ${TOOL_ASN1_COMPILE}                    \
>                 ${ASN1_OPTS.${src}}             \
>                 --option-file=${.ALLSRC:[2]}    \
>                 ${.ALLSRC:[1]} ${src:.asn1=_asn1}
> 
> 
> this rule will run the asn1_compile multiple times when it infact
> only wants to be run once.  i'm not sure how this is causing zero
> length files to be created but this rule is, AFAIK, broken.
> 
> i don't have a fix.
> 
> 
> .mrg.
> 
> ----- End forwarded message -----

i think matt thomas commited something here?  from this file:

revision 1.5
date: 2011/07/27 03:18:52;  author: matt;  state: Exp;  lines: +17 -14
Workaround around make bug by using an intermediate file/rule.


.mrg.