added missing signal constants for espidf

(apply <#3658> to `main`)
(cherry picked from commit 539ec75)

Author: Tevz-Beskovnik

src/unix/newlib/espidf/mod.rs

@@ -89,6 +89,16 @@ pub const MSG_EOR: ::c_int = 0x08;
 
 pub const PTHREAD_STACK_MIN: ::size_t = 768;
 
+pub const SIGABRT: ::size_t = 1;
+pub const SIGFPE: ::size_t = 1;
+pub const SIGILL: ::size_t = 1;
+pub const SIGINT: ::size_t = 1;
+pub const SIGSEGV: ::size_t = 1;
+pub const SIGTERM: ::size_t = 1;
+pub const SIGHUP: ::size_t = 1;
+pub const SIGQUIT: ::size_t = 1;
+pub const NSIG: ::size_t = 2;
+
 extern "C" {
     pub fn pthread_create(
         native: *mut ::pthread_t,