bug#7833: automake uses two different values for DejaGNU srcdir

[Ian Lance Taylor]

When automake is configured to use DejaGNU, it uses two different values
for srcdir.  There are two different cases in lib/am/dejagnu.am:

The first is in check-DEJAGNU:

check-DEJAGNU: site.exp
## Life is easiest with an absolute srcdir, so do that.
        srcdir=`$(am__cd) $(srcdir) && pwd`; export srcdir; \

This value is passed to runtest with a --srcdir option.

The second is in site.exp:

site.exp: Makefile
        @echo 'Making a new site.exp file...'
        @echo '## these variables are automatically generated by make ##' 
>site.tmp
        @echo '# Do not edit here.  If you wish to override these values' 
>>site.tmp
        @echo '# edit the last section' >>site.tmp
        @echo 'set srcdir $(srcdir)' >>site.tmp

This value is read by DejaGNU after option processing is complete,
effectively overwriting the value passed with the --srcdir option.

The value of srcdir stored in site.exp should be an absolute path, just
like the value passed to runtest via --srcdir.

Ian