vmbase: Improve error logging for stack_guard

The rand:: functions return an error so log it while panicking.

Test: TH
Change-Id: I7b87b1230d211249adf19c35244b49b303719813
diff --git a/vmbase/src/entry.rs b/vmbase/src/entry.rs
index 2ff66cc..b19efce 100644
--- a/vmbase/src/entry.rs
+++ b/vmbase/src/entry.rs
@@ -53,8 +53,14 @@
     // We keep a null byte at the top of the stack guard to act as a string terminator.
     let random_guard = &mut stack_guard[..(SIZE_OF_STACK_GUARD - 1)];
 
-    rand::init().expect("Failed to initialize a source of entropy");
-    rand::fill_with_entropy(random_guard).expect("Failed to get stack canary entropy");
+    if let Err(e) = rand::init() {
+        panic!("Failed to initialize a source of entropy: {e}");
+    }
+
+    if let Err(e) = rand::fill_with_entropy(random_guard) {
+        panic!("Failed to get stack canary entropy: {e}");
+    }
+
     bionic::__get_tls().stack_guard = u64::from_ne_bytes(stack_guard);
 
     // Note: If rust_entry ever returned (which it shouldn't by being -> !), the compiler-injected