Building PostgreSQL in external directory is broken?

Hackers,

I usually build the PostgreSQL from the sources directory. But I've
heard a complaint that PostgreSQL can't be built in the external
directory.

Assuming postgres sources located in postgresql directory, the
following sequence of commands

mkdir -p pgbld
cd pgbld
../postgresql/configure --disable-debug --disable-cassert --enable-tap-tests
make -j4

results in an error

.../src/pgbld/../postgresql/src/include/utils/elog.h:73:10: fatal
error: utils/errcodes.h: No such file or directory
73 | #include "utils/errcodes.h"

| ^~~~~~~~~~~~~~~~~~

I've discovered this a bit. It appears that Makefile generates
src/backend/utils/errcodes.h in the build directory, but symlinks
src/include/utils/errcodes.h to the sources directory. That is
src/include/utils/errcodes.h appears to be a broken symlink. I've
written a short patch to fix that.

It seems strange to me that I'm the first one discovering this. Am I
missing something?

------
Regards,
Alexander Korotkov