fix(esp_libc/kconfig): exclude IDF_TARGET_LINUX from LibC menu

On the Linux target the host's C library is used directly; none of the
LibC menu options apply. Mark the entire "LibC" menu as `depends on
!IDF_TARGET_LINUX` so its symbols (LIBC_NEWLIB, LIBC_PICOLIBC, …) stay
undefined on Linux builds.

Also gate the picolibc-specific include in components/console/linenoise/
linenoise.c under `!CONFIG_IDF_TARGET_LINUX` so the file does not try to
pull <stdio-bufio.h> on the host even if CONFIG_LIBC_PICOLIBC is set by
some other build path.

components/console/linenoise/linenoise.c

@@ -124,9 +124,11 @@
 #include <sys/param.h>
 #include <assert.h>
 #include "linenoise.h"
+#if !CONFIG_IDF_TARGET_LINUX
 #if CONFIG_LIBC_PICOLIBC
 #include <stdio-bufio.h>
 #endif
+#endif // !CONFIG_IDF_TARGET_LINUX
 
 #if CONFIG_LIBC_PICOLIBC && !CONFIG_LIBC_PICOLIBC_NEWLIB_COMPATIBILITY
 __thread FILE *linenoise_stdin;

components/esp_libc/Kconfig

@@ -1,4 +1,5 @@
 menu "LibC"
+    depends on !IDF_TARGET_LINUX
 
     choice LIBC
         prompt "LibC to build application with"