package/ibm-sw-tpm2: re-fix build with uClibc-ng and older glibcs

package/ibm-sw-tpm2: re-fix build with uClibc-ng and older glibcs

In commit 26e37cef1627faa1f5ab8935482e2b2bc3465c33, we started using
__WORDSIZE to get the size of longs on the given architecture, in
order to support all CPU architectures.

Unfortunately, __WORDSIZE is not enabled in musl, so in
19bd08900448aa45b506320ad2ab912f789e6e5e, we switched to using
LONG_BIT instead of __WORDSIZE.

However, LONG_BIT is not readily available on glibc, you need
_XOPEN_SOURCE to be defined, which was done in
a34e7f88f67b77066f73894dc8e42bca3c076fa6.

However, in a34e7f88f67b77066f73894dc8e42bca3c076fa6, _XOPEN_SOURCE
was just defined, with no specific value. This caused the build to
break again on uClibc-ng and older glibcs, because clock_gettime() and
CLOCK_MONOTONIC were no longer defined. In both uClibc-ng and glibc,
CLOCK_MONOTONIC is only defined if __USE_POSIX199309 is defined. It
turns out that simply defining _XOPEN_SOURCE with no value does not
lead to __USE_POSIX199309 being defined in uClibc-ng and old glibcs,
while it is defined in newer glibcs.

The difference comes from the following snippet of code, which is
present in recent enough glibc's <feature.h> but not uClibc-ng's or
older glibc's <feature.h>:

/* If none of the ANSI/POSIX macros are defined, or if _DEFAULT_SOURCE
   is defined, use POSIX.1-2008 (or another version depending on
   _XOPEN_SOURCE).  */

So the fact that we are defining _DEFAULT_SOURCE makes it assume that
we're using POSIX 2008.09, which obviously includes POSIX 1993.09.

Due to the lack of this code snippet, uClibc-ng <features.h> only
enables:

     !defined _POSIX_SOURCE && !defined _POSIX_C_SOURCE)

but not:

So we need an _XOPEN_SOURCE level of at least 500 for POSIX 1993.09
definitions to be available.

This is confirmed by the feature_test_macros man page, which states:

                  _XOPEN_SOURCE < 500
                         _POSIX_C_SOURCE is defined with the value 2.

                  500 <= _XOPEN_SOURCE < 600
                         _POSIX_C_SOURCE is defined with the value 199506L.

When this is fixed, another issue arises with older glibc toolchains
(such as Sourcery ARM), where fd_set is no longer defined. Inded, with
POSIX-1.2001 being enabled, we need to include <sys/select.h> to
access the fd_set definition and friends (see man fd_set for details).

This commit was tested with two glibc toolchains (recent and old), one
uClibc-ng toolchain and one musl toolchain.

Fixes:

  http://autobuild.buildroot.net/results/e20f9474fc0217036faa6561df33fa983466ddfe/
  (uClibc-ng)

  http://autobuild.buildroot.net/results/b5d944389fc96ef2c5e0608fe4ac34149e5f9739/
  (glibc)

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
Acked-by: Vincent Fazio <vfazio@gmail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>