When an archive fails to build, print the path

Currently the output on failure is as follows:

       Compiling block-buffer v0.10.4
       Compiling crypto-common v0.1.6
       Compiling digest v0.10.7
       Compiling sha2 v0.10.8
       Compiling xz2 v0.1.7
    error: failed to build archive: No such file or directory

    error: could not compile `bootstrap` (lib) due to 1 previous error

Print which file is being constructed to give some hint about what is
going on.

1 files changed, 3 insertions, 1 deletions

diff --git a/compiler/rustc_codegen_llvm/src/back/archive.rs b/compiler/rustc_codegen_llvm/src/back/archive.rs
index a354f3d3536..eca0ead8666 100644
--- a/compiler/rustc_codegen_llvm/src/back/archive.rs
+++ b/compiler/rustc_codegen_llvm/src/back/archive.rs
@@ -101,7 +101,9 @@ impl<'a> ArchiveBuilder for LlvmArchiveBuilder<'a> {
     fn build(mut self: Box<Self>, output: &Path) -> bool {
         match self.build_with_llvm(output) {
             Ok(any_members) => any_members,
-            Err(e) => self.sess.dcx().emit_fatal(ArchiveBuildFailure { error: e }),
+            Err(error) => {
+                self.sess.dcx().emit_fatal(ArchiveBuildFailure { path: output.to_owned(), error })
+            }
         }
     }
 }