[Libc] add HAVE_SYS_SIGNALS config

components/libc/Kconfig

@@ -29,4 +29,10 @@ if RT_USING_LIBC && RT_USING_DFS
     endif
 endif
 
+config HAVE_SYS_SIGNALS
+    bool "Toolchains/libc has sigval/sigevent structure definitions"
+    default n
+    help
+        Toolchains/libc has sigval/sigevent/siginfo_t definitions.
+
 endmenu