e838a98475 depends: re-enable using -flto when building expat (fanquake)
304452558c depends: expat 2.4.8 (fanquake)
Pull request description:
Currently, when building the expat package in depends, using `-flto` (`LTO=1`), the configure check can fail, because it cannot determine the system endianess:
```bash
configure:18718: result: unknown
configure:18733: error: unknown endianness
presetting ac_cv_c_bigendian=no (or yes) will help
```
Fix that by defining `_DEFAULT_SOURCE`, which in turn defines `__USE_MISC` (`features.h`):
```c
#if defined _DEFAULT_SOURCE
# define __USE_MISC1
#endif
```
which exposes additional definitions in `endian.h`:
```c
#include <features.h>
/* Get the definitions of __*_ENDIAN, __BYTE_ORDER, and __FLOAT_WORD_ORDER. */
#include <bits/endian.h>
#ifdef __USE_MISC
# define LITTLE_ENDIAN__LITTLE_ENDIAN
# define BIG_ENDIAN__BIG_ENDIAN
# define PDP_ENDIAN__PDP_ENDIAN
# define BYTE_ORDER__BYTE_ORDER
#endif
```
and gives us a working configure.
You could test building this change with Guix + LTO with [this branch](https://github.com/fanquake/bitcoin/tree/lto_in_guix). Note that that build may fail for other reasons (on x86_64), unrelated to this change.
Some related upstream discussion:
https://bugs.gentoo.org/757681https://forums.gentoo.org/viewtopic-t-1013786.html
ACKs for top commit:
hebasto:
re-ACK e838a98475, only [suggested](https://github.com/bitcoin/bitcoin/pull/25697#discussion_r929735675) changes since my recent [review](https://github.com/bitcoin/bitcoin/pull/25697#pullrequestreview-1050657421).
jarolrod:
code review ACK e838a98475
Tree-SHA512: 9dbf64c9bd1fd995a4d1addc011ffeff83d50df736030012346c97605e63aed4b5bac390a81abe646c1be28ad6fd600f64560dcb26bbc2edf5d513ca3b180bfa
207a228773