lib/libc: Update picolibc to 1.8.6

 * Reduces memory usage for ctype while fixing an 'isblank'
   related compatibility issue.

 * Resolves compatibility issues with GCC 13

 * Removes explicit _POSIX_C_SOURCE definition when building
   as a module.

 * Fix some _FORTIFY_SOURCE issues.

Signed-off-by: Keith Packard <[email protected]>

Author: keith-packard

west.yml

@@ -310,7 +310,7 @@ manifest:
         - debug
     - name: picolibc
       path: modules/lib/picolibc
-      revision: 1a5c603b9f8e228f9459bdafedad15ea28efc700
+      revision: 764ef4e401a8f4c6a86ab723533841f072885a5b
     - name: segger
       revision: 9d0191285956cef43daf411edc2f1a7788346def
       path: modules/debug/segger