Wrap ttyname_r check in AC_CACHE_CHECK (php#14417)

This enables cross-compiling to set the php_cv_func_ttyname_r variable
for adjusting the configuration manually.

In case of cross-compiling the AC_CHECK_FUNCS is additionally used to
guess whether the target has the ttyname_r. Current platforms mostly
either have working ttyname_r compatible with POSIX or not.

Author: petk

ext/posix/config.m4

@@ -27,24 +27,20 @@ dnl (first argument is not validated and has different error).
   AS_IF([command -v ldd >/dev/null && ldd --version 2>&1 | grep -q "^musl"],[],
     [AC_CHECK_FUNCS(pathconf fpathconf)])
 
-  AC_MSG_CHECKING([for working ttyname_r() implementation])
-  AC_RUN_IFELSE([AC_LANG_SOURCE([[
-#include <unistd.h>
-
-int main(int argc, char *argv[])
-{
-	char buf[64];
-
-	return !ttyname_r(0, buf, 64);
-}
-  ]])],[
-    AC_MSG_RESULT([yes])
-    AC_DEFINE(HAVE_TTYNAME_R, 1, [Whether you have a working ttyname_r])
-  ],[
-    AC_MSG_RESULT([no, posix_ttyname() will be thread-unsafe])
-  ], [
-    AC_MSG_RESULT([no, cannot detect working ttyname_r() when cross compiling. posix_ttyname() will be thread-unsafe])
-  ])
+  AC_CACHE_CHECK([for working ttyname_r() implementation],
+    [php_cv_func_ttyname_r],
+    [AC_RUN_IFELSE([AC_LANG_PROGRAM([#include <unistd.h>], [[
+      char buf[64];
+      return !ttyname_r(0, buf, 64);
+    ]])],
+    [php_cv_func_ttyname_r=yes],
+    [php_cv_func_ttyname_r=no],
+    [AC_CHECK_FUNC([ttyname_r],
+      [php_cv_func_ttyname_r=yes], [php_cv_func_ttyname_r=no])])])
+  AS_VAR_IF([php_cv_func_ttyname_r], [yes],
+    [AC_DEFINE([HAVE_TTYNAME_R], [1],
+      [Define to 1 if you have a working ttyname_r.])],
+    [AC_MSG_NOTICE([posix_ttyname() will be thread-unsafe])])
 
   AC_CHECK_MEMBERS([struct utsname.domainname],,,[
     #ifndef _GNU_SOURCE