Pass type when creating load

This makes load generation compatible with opaque pointers.

The generation of nontemporal copies still accesses the pointer
element type, as fixing this requires more movement.

compiler/rustc_codegen_llvm/src/llvm/ffi.rs

@@ -1385,7 +1385,12 @@ extern "C" {
         Val: &'a Value,
         Name: *const c_char,
     ) -> &'a Value;
-    pub fn LLVMBuildLoad(B: &Builder<'a>, PointerVal: &'a Value, Name: *const c_char) -> &'a Value;
+    pub fn LLVMBuildLoad2(
+        B: &Builder<'a>,
+        Ty: &'a Type,
+        PointerVal: &'a Value,
+        Name: *const c_char,
+    ) -> &'a Value;
 
     pub fn LLVMBuildStore(B: &Builder<'a>, Val: &'a Value, Ptr: &'a Value) -> &'a Value;