Don't probe extra libraries for fdatasync.

Commit d2e15083 got rid of the main configure probe and HAVE_FDATASYNC
macro, but we still searched -lrt and -lposix4 for old Solaris systems.
It's in the C library on modern Solaris, as on other supported systems.

Reviewed-by: Peter Eisentraut <peter@eisentraut.org>
Reviewed-by: Tristan Partin <tristan@neon.tech>
Discussion: https://postgr.es/m/CA%2BhUKGLLVx4drdvXats9PxH3eeB%2BE2NkJReJ%2BRGmaOpU%3D9rgEA%40mail.gmail.com

configure

@@ -12195,63 +12195,6 @@ if test "$ac_res" != no; then :
 
 fi
 
-# Solaris:
-{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for library containing fdatasync" >&5
-$as_echo_n "checking for library containing fdatasync... " >&6; }
-if ${ac_cv_search_fdatasync+:} false; then :
-  $as_echo_n "(cached) " >&6
-else
-  ac_func_search_save_LIBS=$LIBS
-cat confdefs.h - <<_ACEOF >conftest.$ac_ext
-/* end confdefs.h.  */
-
-/* Override any GCC internal prototype to avoid an error.
-   Use char because int might match the return type of a GCC
-   builtin and then its argument prototype would still apply.  */
-#ifdef __cplusplus
-extern "C"
-#endif
-char fdatasync ();
-int
-main ()
-{
-return fdatasync ();
-  ;
-  return 0;
-}
-_ACEOF
-for ac_lib in '' rt posix4; do
-  if test -z "$ac_lib"; then
-    ac_res="none required"
-  else
-    ac_res=-l$ac_lib
-    LIBS="-l$ac_lib  $ac_func_search_save_LIBS"
-  fi
-  if ac_fn_c_try_link "$LINENO"; then :
-  ac_cv_search_fdatasync=$ac_res
-fi
-rm -f core conftest.err conftest.$ac_objext \
-    conftest$ac_exeext
-  if ${ac_cv_search_fdatasync+:} false; then :
-  break
-fi
-done
-if ${ac_cv_search_fdatasync+:} false; then :
-
-else
-  ac_cv_search_fdatasync=no
-fi
-rm conftest.$ac_ext
-LIBS=$ac_func_search_save_LIBS
-fi
-{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $ac_cv_search_fdatasync" >&5
-$as_echo "$ac_cv_search_fdatasync" >&6; }
-ac_res=$ac_cv_search_fdatasync
-if test "$ac_res" != no; then :
-  test "$ac_res" = "none required" || LIBS="$ac_res $LIBS"
-
-fi
-
 # Cygwin:
 { $as_echo "$as_me:${as_lineno-$LINENO}: checking for library containing shmget" >&5
 $as_echo_n "checking for library containing shmget... " >&6; }

configure.ac

@@ -1286,8 +1286,6 @@ AC_SEARCH_LIBS(getopt_long, [getopt gnugetopt])
 AC_SEARCH_LIBS(shm_open, rt)
 AC_SEARCH_LIBS(shm_unlink, rt)
 AC_SEARCH_LIBS(clock_gettime, [rt posix4])
-# Solaris:
-AC_SEARCH_LIBS(fdatasync, [rt posix4])
 # Cygwin:
 AC_SEARCH_LIBS(shmget, cygipc)
 # *BSD:

meson.build

@@ -2421,7 +2421,6 @@ func_checks = [
   # required. Just checking for dlsym() ought to suffice.
   ['dlsym', {'dependencies': [dl_dep], 'define': false}],
   ['explicit_bzero'],
-  ['fdatasync', {'dependencies': [rt_dep, posix4_dep], 'define': false}], # Solaris
   ['getifaddrs'],
   ['getopt', {'dependencies': [getopt_dep, gnugetopt_dep], 'skip': always_replace_getopt}],
   ['getopt_long', {'dependencies': [getopt_dep, gnugetopt_dep], 'skip': always_replace_getopt_long}],