Fix missing errno header on musl build

Backport from kf/wasm3

Author: Keno

src/jloptions.c

@@ -1,6 +1,7 @@
 // This file is a part of Julia. License is MIT: https://julialang.org/license
 
 #include <limits.h>
+#include <errno.h>
 
 #include "julia.h"
 

src/signals-unix.c

@@ -5,6 +5,7 @@
 #include <sys/stat.h>
 #include <sys/mman.h>
 #include <pthread.h>
+#include <errno.h>
 #if defined(_OS_DARWIN_) && !defined(MAP_ANONYMOUS)
 #define MAP_ANONYMOUS MAP_ANON
 #endif