Autoconf: Move getlogin check for HAVE_GETLOGIN to ext/posix (#19058)

This check is related only to ext/posix so it's more clear to have it defined when ext/posix is enabled.

Author: petk

configure.ac

@@ -540,7 +540,6 @@ AC_CHECK_FUNCS(m4_normalize([
  getgrnam_r
  gethostname
  getloadavg
- getlogin
  getprotobyname
  getprotobynumber
  getpwnam_r

ext/posix/config.m4

@@ -17,6 +17,7 @@ if test "$PHP_POSIX" = "yes"; then
  eaccess
  getgrgid_r
  getgroups
+ getlogin
  getpgid
  getrlimit
  getsid