Revert "add crate_root property to rust modules"

Revert submission 2605644-rulebuilder-ninja-vars

Reason for revert: b/299568218

Reverted changes: /q/submissionid:2605644-rulebuilder-ninja-vars

Change-Id: I17645fcff117909c09a016157235805f0974340b
diff --git a/rust/binary.go b/rust/binary.go
index 2c9f64d..1e24beb 100644
--- a/rust/binary.go
+++ b/rust/binary.go
@@ -137,14 +137,9 @@
 
 func (binary *binaryDecorator) compile(ctx ModuleContext, flags Flags, deps PathDeps) buildOutput {
 	fileName := binary.getStem(ctx) + ctx.toolchain().ExecutableSuffix()
+	srcPath, _ := srcPathFromModuleSrcs(ctx, binary.baseCompiler.Properties.Srcs)
 	outputFile := android.PathForModuleOut(ctx, fileName)
 	ret := buildOutput{outputFile: outputFile}
-	var crateRootPath android.Path
-	if binary.baseCompiler.Properties.Crate_root == nil {
-		crateRootPath, _ = srcPathFromModuleSrcs(ctx, binary.baseCompiler.Properties.Srcs)
-	} else {
-		crateRootPath = android.PathForModuleSrc(ctx, *binary.baseCompiler.Properties.Crate_root)
-	}
 
 	flags.RustFlags = append(flags.RustFlags, deps.depFlags...)
 	flags.LinkFlags = append(flags.LinkFlags, deps.depLinkFlags...)
@@ -159,7 +154,7 @@
 	}
 	binary.baseCompiler.unstrippedOutputFile = outputFile
 
-	ret.kytheFile = TransformSrcToBinary(ctx, crateRootPath, deps, flags, outputFile).kytheFile
+	ret.kytheFile = TransformSrcToBinary(ctx, srcPath, deps, flags, outputFile).kytheFile
 	return ret
 }