posix: options: define threadsafe fns in terms of option groups

The functions associated with the _POSIX_THREAD_SAFE_FUNCTIONS
Option are members of other POSIX Option Groups. Specifically,
POSIX_C_LANG_SUPPORT_R, POSIX_FILE_LOCKING, POSIX_FILE_SYSTEM_R,
and POSIX_SYSTEM_DATABASE_R.

Moreover, _POSIX_THREAD_SAFE_FUNCTIONS is required to be
available with any conforming implementation.

Therefore, it does not make sense to have a Kconfig option to
turn it off or on; it should be enabled or disabled based on
whether the required POSIX Option Groups are active.

Signed-off-by: Chris Friedt <cfriedt@tenstorrent.com>

Author: cfriedt

include/zephyr/posix/posix_features.h

@@ -161,7 +161,8 @@
 /* #define _POSIX_THREAD_ROBUST_PRIO_INHERIT (-1L) */
 /* #define _POSIX_THREAD_ROBUST_PRIO_PROTECT (-1L) */
 
-#ifdef CONFIG_POSIX_THREAD_SAFE_FUNCTIONS
+#if defined(CONFIG_POSIX_C_LANG_SUPPORT_R) && defined(CONFIG_POSIX_FILE_LOCKING) &&                \
+	defined(CONFIG_POSIX_FILE_SYSTEM_R) && defined(CONFIG_POSIX_SYSTEM_DATABASE_R)
 #define _POSIX_THREAD_SAFE_FUNCTIONS _POSIX_VERSION
 #endif
 

lib/posix/options/Kconfig.pthread

@@ -159,8 +159,11 @@ config POSIX_THREAD_PRIO_PROTECT
 
 config POSIX_THREAD_SAFE_FUNCTIONS
 	bool "POSIX thread-safe functions"
-	select POSIX_FILE_SYSTEM_R
 	select POSIX_C_LANG_SUPPORT_R
+	select POSIX_FILE_LOCKING
+	select POSIX_FILE_SYSTEM_R
+	select POSIX_SYSTEM_DATABASE_R
+	select POSIX_SYNCHRONIZED_IO
 	help
 	  Select 'y' here to enable POSIX thread-safe functions including asctime_r(), ctime_r(),
 	  flockfile(), ftrylockfile(), funlockfile(), getc_unlocked(), getchar_unlocked(),