cd to / before running soong_build .

This lets one avoid any decisions as to when to chdir there during its
execution and leads to better sandboxing because the pwd doesn't leak to
init() functions anymore.

Test: Manual.
Change-Id: I1560da8ed3a621249426f9e8908aa890c21e13ba

shared/Android.bp

@@ -8,6 +8,10 @@ bootstrap_go_package {
     srcs: [
         "env.go",
         "paths.go",
+        "debug.go",
+    ],
+    testSrcs: [
+        "paths_test.go",
     ],
     deps: [
         "soong-bazel",

shared/debug.go

@@ -0,0 +1,17 @@
+package shared
+
+import (
+	"os"
+	"os/exec"
+)
+
+// Finds the Delve binary to use. Either uses the SOONG_DELVE_PATH environment
+// variable or if that is unset, looks at $PATH.
+func ResolveDelveBinary() string {
+	result := os.Getenv("SOONG_DELVE_PATH")
+	if result == "" {
+		result, _ = exec.LookPath("dlv")
+	}
+
+	return result
+}

shared/env.go

@@ -91,6 +91,28 @@ func StaleEnvFile(filepath string, getenv func(string) string) (bool, error) {
 	return false, nil
 }
 
+// Deserializes and environment serialized by EnvFileContents() and returns it
+// as a map[string]string.
+func EnvFromFile(envFile string) (map[string]string, error) {
+	result := make(map[string]string)
+	data, err := ioutil.ReadFile(envFile)
+	if err != nil {
+		return result, err
+	}
+
+	var contents envFileData
+	err = json.Unmarshal(data, &contents)
+	if err != nil {
+		return result, err
+	}
+
+	for _, entry := range contents {
+		result[entry.Key] = entry.Value
+	}
+
+	return result, nil
+}
+
 // Implements sort.Interface so that we can use sort.Sort on envFileData arrays.
 func (e envFileData) Len() int {
 	return len(e)

shared/paths.go

@@ -30,6 +30,21 @@ type SharedPaths interface {
 	BazelMetricsDir() string
 }
 
+// Joins the path strings in the argument list, taking absolute paths into
+// account. That is, if one of the strings is an absolute path, the ones before
+// are ignored.
+func JoinPath(base string, rest ...string) string {
+	result := base
+	for _, next := range rest {
+		if filepath.IsAbs(next) {
+			result = next
+		} else {
+			result = filepath.Join(result, next)
+		}
+	}
+	return result
+}
+
 // Given the out directory, returns the root of the temp directory (to be cleared at the start of each execution of Soong)
 func TempDirForOutDir(outDir string) (tempPath string) {
 	return filepath.Join(outDir, ".temp")

shared/paths_test.go

@@ -0,0 +1,32 @@
+// Copyright 2021 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 shared
+
+import (
+	"testing"
+)
+
+func assertEqual(t *testing.T, expected, actual string) {
+	t.Helper()
+	if expected != actual {
+		t.Errorf("expected %q != got %q", expected, actual)
+	}
+}
+
+func TestJoinPath(t *testing.T) {
+	assertEqual(t, "/a/b", JoinPath("c/d", "/a/b"))
+	assertEqual(t, "a/b", JoinPath("a", "b"))
+	assertEqual(t, "/a/b", JoinPath("x", "/a", "b"))
+}