internal/getproviders: SearchLocalDirectory can handle symlinks

Previously this was failing to treat symlinks to directories as unpacked
layout, because our file info was only an Lstat result, not a full Stat.

Now we'll resolve the symlink first, allowing us to handle a symlink to
a directory. That's important because our internal/providercache behavior
is to symlink from one cache to another where possible.

internal/getproviders/filesystem_search.go

@@ -68,6 +68,15 @@ func SearchLocalDirectory(baseDir string) (map[addrs.Provider]PackageMetaList, e
 			providerAddr = addrs.NewProvider(hostname, namespace, typeName)
 		}
 
+		// The "info" passed to our function is an Lstat result, so it might
+		// be referring to a symbolic link. We'll do a full "Stat" on it
+		// now to make sure we're making tests against the real underlying
+		// filesystem object below.
+		info, err = os.Stat(fullPath)
+		if err != nil {
+			return fmt.Errorf("failed to read metadata about %s: %s", fullPath, err)
+		}
+
 		switch len(parts) {
 		case 5: // Might be unpacked layout
 			if !info.IsDir() {