Revert "Sandbox soong_build by changing to root directory"

This reverts commit 05c25ccb4adb5329add700b533416c226cdbfa96.

Reason for revert: broke absolute OUT_DIR
Bug: 146437378

Change-Id: I523ed79d40e1c1ef040212ba794a7a084abea75d
diff --git a/android/makevars.go b/android/makevars.go
index aba4cce..38a028c 100644
--- a/android/makevars.go
+++ b/android/makevars.go
@@ -23,6 +23,7 @@
 	"strings"
 
 	"github.com/google/blueprint"
+	"github.com/google/blueprint/pathtools"
 	"github.com/google/blueprint/proptools"
 )
 
@@ -40,6 +41,7 @@
 	Config() Config
 	DeviceConfig() DeviceConfig
 	AddNinjaFileDeps(deps ...string)
+	Fs() pathtools.FileSystem
 
 	ModuleName(module blueprint.Module) string
 	ModuleDir(module blueprint.Module) string
@@ -149,8 +151,7 @@
 		return
 	}
 
-	outFile := absolutePath(PathForOutput(ctx,
-		"make_vars"+proptools.String(ctx.Config().productVariables.Make_suffix)+".mk").String())
+	outFile := PathForOutput(ctx, "make_vars"+proptools.String(ctx.Config().productVariables.Make_suffix)+".mk").String()
 
 	if ctx.Failed() {
 		return
@@ -174,15 +175,15 @@
 
 	outBytes := s.writeVars(vars)
 
-	if _, err := os.Stat(absolutePath(outFile)); err == nil {
-		if data, err := ioutil.ReadFile(absolutePath(outFile)); err == nil {
+	if _, err := os.Stat(outFile); err == nil {
+		if data, err := ioutil.ReadFile(outFile); err == nil {
 			if bytes.Equal(data, outBytes) {
 				return
 			}
 		}
 	}
 
-	if err := ioutil.WriteFile(absolutePath(outFile), outBytes, 0666); err != nil {
+	if err := ioutil.WriteFile(outFile, outBytes, 0666); err != nil {
 		ctx.Errorf(err.Error())
 	}
 }