Build libc6-2.28 from source: ld-2.28.so cause errors when installing deb package

[Florian Weimer]

* Kenny Bian via Libc-help:

> We try to build libc6-2.28 from source code. Our board runs Ubuntu
> 18.04 in armhf architecture. We downloaded the source code from
> https://launchpad.net/ubuntu/+source/glibc/2.28-0ubuntu1.
> Here is what we did to create the deb package:
> 1. We build it by using these bash commands:
> /usr/bin/dpkg-source -x glibc_2.28-0ubuntu1.dsc libc6-2.28
> pushd libc6-2.28/
> mkdir build
> pushd build/
> ../configure \
>     --host=arm-linux-gnueabihf \
>     --prefix=/tmp/armhf/libc6/usr \
>     --enable-obsolete-nsl
> make
> make install

make install without a temporary DESTDIR is not supported.
Unfortunately the instructions do not make this clear.

The issue is that make uses separate commands for installing files, and
half-way through the update, the system is in an inconsistent state and
further commands fail, and the installation is not able to complete as a
result.

Using a temporary directory with DESTDIR and then rsync avoids the issue
(cp truncates the destination file, causing other issues).

Thanks,
Florian