Add unsafe to more extern "C" blocks. (#162)

Author: sunfishcode

src/program/linux_raw.rs

@@ -112,7 +112,7 @@ pub(super) unsafe extern "C" fn entry(mem: *mut usize) -> ! {
 
             // The linker-generated symbols that mark the start and end of the
             // `.init_array` section.
-            extern "C" {
+            unsafe extern "C" {
                 static __init_array_start: c_void;
                 static __init_array_end: c_void;
             }
@@ -307,7 +307,7 @@ pub fn exit(status: c_int) -> ! {
 
         // The linker-generated symbols that mark the start and end of the
         // `.fini_array` section.
-        extern "C" {
+        unsafe extern "C" {
             static __fini_array_start: c_void;
             static __fini_array_end: c_void;
         }