When PATH_MAX is undefined, realpath cannot ever ENAMETOOLONG, so
this test is unsupported.

On GCC before 11, IPA can make the fortified realpath aware that the
buffer size is not large enough (8 bytes instead of PATH_MAX bytes).
Fix this by using a buffer that is large enough.

Since the _FORTIFY_SOURCE feature uses some routines of Glibc, they need to
be excluded from the fortification.

On top of that:
 - some tests explicitly verify that some level of fortification works
   appropriately, we therefore shouldn't modify the level set for them.
 - some objects need to be build with optimization disabled, which
   prevents _FORTIFY_SOURCE to be used for them.

Assembler files that implement architecture specific versions of the
fortified routines were not excluded from _FORTIFY_SOURCE as there is no
C header included that would impact their behavior.

Reviewed-by: Siddhesh Poyarekar <siddhesh@sourceware.org>

Use malloc rather than alloca to avoid potential stack overflow.

Reviewed-by: Adhemerval Zanella  <adhemerval.zanella@linaro.org>

ISO C2x defines scanf %b for input of binary integers (with an
optional 0b or 0B prefix).  Implement such support, along with the
corresponding SCNb* macros in <inttypes.h>.  Unlike the support for
binary integers with 0b or 0B prefix with scanf %i, this is supported
in all versions of scanf (independent of the standards mode used for
compilation), because there are no backwards compatibility concerns
(%b wasn't previously a supported format) the way there were for %i.

Tested for x86_64 and x86.

There is no fork detection on current arc4random implementation, so
use lower subprocess on fork tests.  The tests now run on 0.1s
instead of 8s on a Ryzen9 5900X.

Checked on x86_64-linux-gnu.
Reviewed-by: Carlos O'Donell <carlos@redhat.com>

With fortification enabled, few function calls return result need to be
checked, has they get the __wur macro enabled.

Reviewed-by: Siddhesh Poyarekar <siddhesh@sourceware.org>