APR Makefile bug when building outside the source tree

[Julian Foad <ju...@btopenworld.com>]

In apr/Makefile.in and apr-util/Makefile.in, the three files
 exports.c
 export_vars.h
 apr[util].exp
are not specified as being in a particular directory (${srcdir} or whatever), and so the build does not work properly outside the source tree:

~/build/subversion/apr-util> make
[...]
make[1]: Entering directory `/home/julianfoad/build/subversion/apr-util'
gcc -E -DHAVE_CONFIG_H -DLINUX=2 -D_REENTRANT -D_XOPEN_SOURCE=500 -D_BSD_SOURCE -D_SVID_SOURCE -D_GNU_SOURCE   -I/home/julianfoad/build/subversion/apr-util/include -I/home/julianfoad/build/subversion/apr-util/include/private -I/home/julianfoad/src/subversion/apr-util/include/private -I/home/julianfoad/src/subversion/apr-util/include  -I/home/julianfoad/build/subversion/apr/include -I/home/julianfoad/src/subversion/apr/include    exports.c | grep "ap_hack_" | sed -e 's/^.*[)]\(.*\);$/\1/' >> aprutil.exp
gcc: exports.c: No such file or directory

I had a quick go at fixing this, but don't understand it well enough.  I have been building in a separate directory for months, but only noticed this recently.  I don't know whether this is a recent regression.  It doesn't stop my Subversion build from proceeding.

p.s. While we're in apr/Makefile.in, a few lines further down, by the target "docs" is a comment "# DON'T REMOVE THIS".  If that were replaced with an intelligent comment saying WHY the rule is important, that would be much more useful.

I am not subscribed to apr-devel.  I have also sent this to dev@subversion.tigris.org.

- Julian