Auto merge of #7749 - iu0zjp2:patch-1, r=ehuss

Fix debug message.

The [path] field of [Fingerprint] contains the "Hash of the path to the base source file".

repro:
```
$ cargo new a
$ cd a
$ echo 'cfg-if="0"' >> Cargo.toml
$ CARGO_HOME=cargo1 cargo build
$ mv cargo1 cargo2
$ CARGO_LOG=cargo::core::compiler::fingerprint=trace CARGO_HOME=cargo2 cargo build
[...]
[... INFO  cargo::core::compiler::fingerprint]     err: path to the compiler has changed
```

Author: bors

src/cargo/core/compiler/fingerprint.rs

@@ -643,7 +643,7 @@ impl Fingerprint {
             bail!("target configuration has changed")
         }
         if self.path != old.path {
-            bail!("path to the compiler has changed")
+            bail!("path to the source has changed")
         }
         if self.profile != old.profile {
             bail!("profile configuration has changed")