Update error messages for failed globs.

Currently error messages appear like:
&fs.PathError{Op:"open", Path:"..." Err:0x18}
which make them difficult to parse.

Test: CI
Change-Id: I18da18abc43230d0ea37d166179d07e585077f51
diff --git a/rust/library.go b/rust/library.go
index baac3f0..62eaefd 100644
--- a/rust/library.go
+++ b/rust/library.go
@@ -773,9 +773,10 @@
 	// Glob together the headers from the modules include_dirs property
 	for _, path := range android.CopyOfPaths(l.includeDirs) {
 		dir := path.String()
-		glob, err := ctx.GlobWithDeps(dir+"/**/*", nil)
+		globDir := dir + "/**/*"
+		glob, err := ctx.GlobWithDeps(globDir, nil)
 		if err != nil {
-			ctx.ModuleErrorf("glob failed: %#v", err)
+			ctx.ModuleErrorf("glob of %q failed: %s", globDir, err)
 			return
 		}