lib: posix: Add top-level define for all POSIX APIs - CONFIG_POSIX_API

It so happened that previously CONFIG_PTHREAD_IPC served this role.
But pthreads and IPC is only parts of POSIX, orthogonal to other
services.

Move CONFIG_POSIX_FS, etc. out from CONFIG_PTHREAD_IPC.

Signed-off-by: Paul Sokolovsky <paul.sokolovsky@linaro.org>

lib/CMakeLists.txt

@@ -7,6 +7,6 @@ endif()
 add_subdirectory_if_kconfig(ring_buffer)
 add_subdirectory_if_kconfig(base64)
 add_subdirectory(mempool)
-add_subdirectory_ifdef(CONFIG_PTHREAD_IPC          posix)
+add_subdirectory_ifdef(CONFIG_POSIX_API            posix)
 add_subdirectory_ifdef(CONFIG_CMSIS_RTOS_V1        cmsis_rtos_v1)
 add_subdirectory(rbtree)

lib/posix/Kconfig

@@ -4,6 +4,14 @@
 # SPDX-License-Identifier: Apache-2.0
 #
 
+config POSIX_API
+	bool "POSIX APIs"
+	help
+	  Enable mostly-standards-compliant implementations of
+	  various POSIX (IEEE 1003.1) APIs.
+
+if POSIX_API
+
 config PTHREAD_IPC
 	bool "POSIX pthread IPC API"
 	help
@@ -26,6 +34,8 @@ config SEM_VALUE_MAX
 	help
 	  Maximum semaphore count in POSIX compliant Application.
 
+endif # PTHREAD_IPC
+
 config MAX_TIMER_COUNT
 	int "Maximum timer count in POSIX application"
 	default 5
@@ -76,4 +86,4 @@ config	POSIX_MAX_OPEN_FILES
 endif
 endif
 
-endif
+endif # POSIX_API