[BUG] glibs tries to install bogus /usr/include/stdlib.h when "make check" is run twice

[Florian Weimer]

* Joseph Myers:

> On Wed, 14 Dec 2016, Markus Trippelsdorf wrote:
>
>> (My sourceware.org/bugzilla/ account got blocked due to bogus SPAM
>> warning. So I send the report directly to the list.)
>> 
>> When one runs "make check" twice in a row, glibc tries to install
>> an internal header file to /usr/include/stdlib.h, e.g.:
>
> We've had problems reported before with bad attempts to install to system 
> header directories, e.g. bug 13810.
>
> The strategy of installing via Makefile targets in the name of installed 
> files seems fragile in that way.  It's also problematic in other ways.  
> When adding build-many-glibcs.py support for stripping installed shared 
> libraries, it occurred to me that really we should have "make 
> install-strip" support that build-many-glibcs.py could use - that's a 
> standard target from the GNU Coding Standards.  But having a single target 
> defining how to create an installed file is in tension with the correct 
> way to install it depending on whether you ran "make install" or "make 
> install-strip".

Right.  In addition, we should guard against “make install” with
DESTDIR="", so that developers do not corrupt their host system if the
installed ld.so is incompatible with the new libc.so or vice versa.