Always print the PKG_CONFIG_PATH in verbose mode

This way is possible to do
```
$ export `cargo cbuild -v 2>&1 | grep PKG_CONFIG_PATH | cut -f 2 -d ' '`
```
To use the pkg-config file in uninstalled mode.

src/build.rs

@@ -66,8 +66,6 @@ fn copy_prebuilt_include_file(
 ) -> anyhow::Result<()> {
     let mut shell = ws.gctx().shell();
     shell.status("Populating", "uninstalled header directory")?;
-    let path = &format!("PKG_CONFIG_PATH=\"{}\"", root_output.display());
-    shell.verbose(move |s| s.note(path))?;
     for (from, to) in build_targets.extra.include.iter() {
         let to = root_output.join("include").join(to);
         create_dir_all(to.parent().unwrap())?;
@@ -1244,6 +1242,11 @@ pub fn cbuild(
             // It is not a new build, recover the static_libs value from the cache
             cpkg.finger_print.static_libs = cpkg.finger_print.load_previous()?.static_libs;
         }
+
+        ws.gctx().shell().verbose(|s| {
+            let path = &format!("PKG_CONFIG_PATH=\"{}\"", root_output.display());
+            s.note(path)
+        })?;
     }
 
     Ok((members, compile_opts))