Change Details

``` Don't assume that `posix_fallocate()` is available on Linux and not available on other operating systems. At least FreeBSD has it and we are not using it. Properly check whether `posix_fallocate()` is present and use it if it is. ``` Backport of core PR18437.

``` Don't assume that `posix_fallocate()` is available on Linux and not available on other operating systems. At least FreeBSD has it and we are not using it. Properly check whether `posix_fallocate()` is present and use it if it is. ``` Backport of core [[https://github.com/bitcoin/bitcoin/pull/18437 | PR18437]].

``` Don't assume that `posix_fallocate()` is available on Linux and not available on other operating systems. At least FreeBSD has it and we are not using it. Properly check whether `posix_fallocate()` is present and use it if it is. ``` Backport of core [[https://github.com/bitcoin/bitcoin/pull/18437 | PR18437]].