Split long lines of variables generated by '+='?

[Simon Josefsson]

I have a generated Automake makefile snippet that does something like:

gdoc_TEXINFOS += texi/ap.c.texi
gdoc_TEXINFOS += texi/shishi_ap.texi
gdoc_MANS += man/shishi_ap.3
gdoc_TEXINFOS += texi/shishi_ap_etype.texi
gdoc_MANS += man/shishi_ap_etype.3
gdoc_TEXINFOS += texi/shishi_ap_nosubkey.texi
...

I believe automake tries to put all names on the same line:

gdoc_TEXINFOS = texi/ap.c.texi texi/shishi_ap.texi ...
gdoc_MANS = man/shishi_ap.3 man/shishi_ap_etype.3 ...

Now, these lines get rather long (about 20KB).  Some make
implementations (alphaev67-dec-osf5.1, alphaev68-dec-osf5.1) cannot
handle this and crashes.

I have verified that everything works if I wrap the line so each line
is at most 1000 characters:

gdoc_TEXINFOS = texi/ap.c.texi texi/shishi_ap.texi ... \
              texi/shishi_ap_req_process_keyusage.texi ... \
              ...


I did not try to find an upper line length limit...

I don't know if automake should care about these broken tools (I have
reported it), but having 20KB long lines is not very nice either.

Thanks,
Simon