Improve ICE message when data-layouts don't match

LLVM target name does not necessarily match the Rust target name and it
can be confusing when the ICE message is describing a target other than
has been specified on the command line.

compiler/rustc_codegen_llvm/src/context.rs

@@ -149,11 +149,12 @@ pub unsafe fn create_module(
 
         if !custom_llvm_used && target_data_layout != llvm_data_layout {
             bug!(
-                "data-layout for builtin `{}` target, `{}`, \
-                  differs from LLVM default, `{}`",
-                sess.target.llvm_target,
-                target_data_layout,
-                llvm_data_layout
+                "data-layout for target `{rustc_target}`, `{rustc_layout}`, \
+                  differs from LLVM target's `{llvm_target}` default layout, `{llvm_layout}`",
+                rustc_target = sess.opts.target_triple,
+                rustc_layout = target_data_layout,
+                llvm_target = sess.target.llvm_target,
+                llvm_layout = llvm_data_layout
             );
         }
     }