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
diff --git a/android/env.go b/android/env.go
index a8c7777..58ad0b6 100644
--- a/android/env.go
+++ b/android/env.go
@@ -17,7 +17,6 @@
 import (
 	"fmt"
 	"os"
-	"os/exec"
 	"strings"
 	"syscall"
 
@@ -34,37 +33,27 @@
 var originalEnv map[string]string
 var soongDelveListen string
 var soongDelvePath string
-var soongDelveEnv []string
+var isDebugging bool
 
-func init() {
-	// Delve support needs to read this environment variable very early, before NewConfig has created a way to
-	// access originalEnv with dependencies.  Store the value where soong_build can find it, it will manually
-	// ensure the dependencies are created.
-	soongDelveListen = os.Getenv("SOONG_DELVE")
-	soongDelvePath = os.Getenv("SOONG_DELVE_PATH")
-	if soongDelvePath == "" {
-		soongDelvePath, _ = exec.LookPath("dlv")
+func InitEnvironment(envFile string) {
+	var err error
+	originalEnv, err = shared.EnvFromFile(envFile)
+	if err != nil {
+		panic(err)
 	}
 
-	originalEnv = make(map[string]string)
-	soongDelveEnv = []string{}
-	for _, env := range os.Environ() {
-		idx := strings.IndexRune(env, '=')
-		if idx != -1 {
-			originalEnv[env[:idx]] = env[idx+1:]
-			if env[:idx] != "SOONG_DELVE" && env[:idx] != "SOONG_DELVE_PATH" {
-				soongDelveEnv = append(soongDelveEnv, env)
-			}
-		}
-	}
-
-	// Clear the environment to prevent use of os.Getenv(), which would not provide dependencies on environment
-	// variable values.  The environment is available through ctx.Config().Getenv, ctx.Config().IsEnvTrue, etc.
-	os.Clearenv()
+	soongDelveListen = originalEnv["SOONG_DELVE"]
+	soongDelvePath = originalEnv["SOONG_DELVE_PATH"]
 }
 
+// Returns whether the current process is running under Delve due to
+// ReexecWithDelveMaybe().
+func IsDebugging() bool {
+	return isDebugging
+}
 func ReexecWithDelveMaybe() {
-	if soongDelveListen == "" {
+	isDebugging = os.Getenv("SOONG_DELVE_REEXECUTED") == "true"
+	if isDebugging || soongDelveListen == "" {
 		return
 	}
 
@@ -72,6 +61,17 @@
 		fmt.Fprintln(os.Stderr, "SOONG_DELVE is set but failed to find dlv")
 		os.Exit(1)
 	}
+
+	soongDelveEnv := []string{}
+	for _, env := range os.Environ() {
+		idx := strings.IndexRune(env, '=')
+		if idx != -1 {
+			soongDelveEnv = append(soongDelveEnv, env)
+		}
+	}
+
+	soongDelveEnv = append(soongDelveEnv, "SOONG_DELVE_REEXECUTED=true")
+
 	dlvArgv := []string{
 		soongDelvePath,
 		"--listen=:" + soongDelveListen,
@@ -88,17 +88,6 @@
 	os.Exit(1)
 }
 
-// getenv checks either os.Getenv or originalEnv so that it works before or after the init()
-// function above.  It doesn't add any dependencies on the environment variable, so it should
-// only be used for values that won't change.  For values that might change use ctx.Config().Getenv.
-func getenv(key string) string {
-	if originalEnv == nil {
-		return os.Getenv(key)
-	} else {
-		return originalEnv[key]
-	}
-}
-
 func EnvSingleton() Singleton {
 	return &envSingleton{}
 }
@@ -108,7 +97,7 @@
 func (c *envSingleton) GenerateBuildActions(ctx SingletonContext) {
 	envDeps := ctx.Config().EnvDeps()
 
-	envFile := PathForOutput(ctx, ".soong.environment")
+	envFile := PathForOutput(ctx, "soong.environment.used")
 	if ctx.Failed() {
 		return
 	}