Revert "Convert package to filepath"

This reverts commit 904958f.

java/gazelle/generate.go

@@ -134,18 +134,17 @@ func (l javaLang) GenerateRules(args language.GenerateArgs) language.GenerateRes
 			}
 			allPackageNames.Add(mJavaPkg.Name)
 
-			mRelFilepath := filepath.FromSlash(mRel)
 			if !mJavaPkg.TestPackage {
 				addNonLocalImportsAndExports(productionJavaImports, nonLocalJavaExports, mJavaPkg.ImportedClasses, mJavaPkg.ImportedPackagesWithoutSpecificClasses, mJavaPkg.ExportedClasses, mJavaPkg.Name, javaClassNamesFromFileNames)
 				for _, f := range mJavaPkg.Files.SortedSlice() {
-					productionJavaFiles.Add(filepath.Join(mRelFilepath, f))
+					productionJavaFiles.Add(filepath.Join(mRel, f))
 				}
 				allMains.AddAll(mJavaPkg.Mains)
 			} else {
 				// Tests don't get to export things, as things shouldn't depend on them.
 				addNonLocalImportsAndExports(testJavaImports, nil, mJavaPkg.ImportedClasses, mJavaPkg.ImportedPackagesWithoutSpecificClasses, mJavaPkg.ExportedClasses, mJavaPkg.Name, javaClassNamesFromFileNames)
 				for _, f := range mJavaPkg.Files.SortedSlice() {
-					path := filepath.Join(mRelFilepath, f)
+					path := filepath.Join(mRel, f)
 					file := javaFile{
 						pathRelativeToBazelWorkspaceRoot: path,
 						pkg:                              mJavaPkg.Name,
@@ -164,7 +163,7 @@ func (l javaLang) GenerateRules(args language.GenerateArgs) language.GenerateRes
 		}
 		allMains.AddAll(javaPkg.Mains)
 		for _, f := range javaFilenamesRelativeToPackage {
-			path := filepath.Join(filepath.FromSlash(args.Rel), f)
+			path := filepath.Join(args.Rel, f)
 			if javaPkg.TestPackage {
 				file := javaFile{
 					pathRelativeToBazelWorkspaceRoot: path,