fix(newlib): Allow for timefunc customization if not impl

Related https://github.com/espressif/esp-idf/issues/11873

components/newlib/Kconfig

@@ -12,7 +12,7 @@ menu "Newlib"
 
             LF: no modification is applied, stdout is sent as is
 
-            CR: each occurence of LF is replaced with CR
+            CR: each occurrence of LF is replaced with CR
 
             This option doesn't affect behavior of the UART driver (drivers/uart.h).
 
@@ -36,7 +36,7 @@ menu "Newlib"
 
             LF: no modification is applied, input is sent to stdin as is
 
-            CR: each occurence of CR is replaced with LF
+            CR: each occurrence of CR is replaced with LF
 
             This option doesn't affect behavior of the UART driver (drivers/uart.h).
 
@@ -93,7 +93,12 @@ menu "Newlib"
                 resolution. Also the gettimeofday function itself may take
                 longer to run.
             - If no timers are used, gettimeofday and time functions
-                return -1 and set errno to ENOSYS.
+                return -1 and set errno to ENOSYS; they are defined as weak,
+                so they could be overridden.
+                If you want to customize gettimeofday() and other time functions,
+                please choose this option and refer to the 'time.c' source file
+                for the exact prototypes of these functions.
+
             - When RTC is used for timekeeping, two RTC_STORE registers are
                 used to keep time in deep sleep mode.