Move ELF build-id reader into a separate library.

Bug: 328702178
Change-Id: I188a8d20d22e67e4f0c7e3441e3781fff369c828

cmd/symbols_map/Android.bp

@@ -5,17 +5,16 @@ package {
 blueprint_go_binary {
     name: "symbols_map",
     srcs: [
-        "elf.go",
         "r8.go",
         "symbols_map.go",
     ],
     testSrcs: [
-        "elf_test.go",
         "r8_test.go",
     ],
     deps: [
         "blueprint-pathtools",
         "golang-protobuf-encoding-prototext",
+        "soong-elf",
         "soong-response",
         "symbols_map_proto",
     ],

cmd/symbols_map/symbols_map.go

@@ -22,6 +22,7 @@ import (
 	"strings"
 
 	"android/soong/cmd/symbols_map/symbols_map_proto"
+	"android/soong/elf"
 	"android/soong/response"
 
 	"github.com/google/blueprint/pathtools"
@@ -116,7 +117,7 @@ func main() {
 	if *elfFile != "" {
 		typ = symbols_map_proto.Mapping_ELF
 		location = *elfFile
-		identifier, err = elfIdentifier(*elfFile, true)
+		identifier, err = elf.Identifier(*elfFile, true)
 		if err != nil {
 			fmt.Fprintf(os.Stderr, "error reading elf identifier: %s\n", err)
 			os.Exit(1)

elf/Android.bp

@@ -0,0 +1,28 @@
+// Copyright 2016 Google Inc. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package {
+    default_applicable_licenses: ["Android-Apache-2.0"],
+}
+
+bootstrap_go_package {
+    name: "soong-elf",
+    pkgPath: "android/soong/elf",
+    srcs: [
+        "elf.go",
+    ],
+    testSrcs: [
+        "elf_test.go",
+    ],
+}

elf/elf.go

@@ -12,7 +12,7 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-package main
+package elf
 
 import (
 	"debug/elf"
@@ -26,9 +26,9 @@ import (
 
 const gnuBuildID = "GNU\x00"
 
-// elfIdentifier extracts the elf build ID from an elf file.  If allowMissing is true it returns
+// Identifier extracts the elf build ID from an elf file.  If allowMissing is true it returns
 // an empty identifier if the file exists but the build ID note does not.
-func elfIdentifier(filename string, allowMissing bool) (string, error) {
+func Identifier(filename string, allowMissing bool) (string, error) {
 	f, err := os.Open(filename)
 	if err != nil {
 		return "", fmt.Errorf("failed to open %s: %w", filename, err)

elf/elf_test.go

@@ -12,7 +12,7 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-package main
+package elf
 
 import (
 	"bytes"