VPath Build Errors

Hey,

I've been building in the git repo just fine but wanted to use vpath builds
so I could keep both "maked" v14 and v15 binaries around, ready to be
installed.

The attached log is result of (while in the versioned directory, a sibling
of the git repo)
`../postgresql/configure`
`make`
`tree`

stdout and stderr output tee'd to a file.

Per the instructions here:

https://www.postgresql.org/docs/current/install-procedure.html

The last handful of lines for make are below:

Thanks!

David J.

cat: ../../src/timezone/objfiles.txt: No such file or directory
cat: jit/objfiles.txt: No such file or directory
gcc -Wall -Wmissing-prototypes [...see file...] -Wl,--as-needed
-Wl,-rpath,'/usr/local/pgsql/lib',--enable-new-dtags -Wl,-E -lz -lpthread
-lrt -ldl -lm -o postgres
gcc: error: replication/backup_manifest.o: No such file or directory
gcc: error: replication/basebackup.o: No such file or directory
gcc: error: replication/basebackup_copy.o: No such file or directory
gcc: error: replication/basebackup_gzip.o: No such file or directory
gcc: error: replication/basebackup_lz4.o: No such file or directory
gcc: error: replication/basebackup_zstd.o: No such file or directory
gcc: error: replication/basebackup_progress.o: No such file or directory
gcc: error: replication/basebackup_server.o: No such file or directory
gcc: error: replication/basebackup_sink.o: No such file or directory
gcc: error: replication/basebackup_target.o: No such file or directory
gcc: error: replication/basebackup_throttle.o: No such file or directory
gcc: error: replication/repl_gram.o: No such file or directory
gcc: error: replication/slot.o: No such file or directory
gcc: error: replication/slotfuncs.o: No such file or directory
gcc: error: replication/syncrep.o: No such file or directory
gcc: error: replication/syncrep_gram.o: No such file or directory
gcc: error: replication/walreceiver.o: No such file or directory
gcc: error: replication/walreceiverfuncs.o: No such file or directory
gcc: error: replication/walsender.o: No such file or directory
gcc: error: utils/fmgrtab.o: No such file or directory
make[2]: *** [Makefile:66: postgres] Error 1
make[2]: Leaving directory '/home/vagrant/pgsql15/src/backend'
make[1]: *** [Makefile:42: all-backend-recurse] Error 2
make[1]: Leaving directory '/home/vagrant/pgsql15/src'
make: *** [GNUmakefile:11: all-src-recurse] Error 2