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/toolchain_library.go b/rust/toolchain_library.go
index e118f92..801c0c2 100644
--- a/rust/toolchain_library.go
+++ b/rust/toolchain_library.go
@@ -40,10 +40,8 @@
 }
 
 type toolchainLibraryProperties struct {
-	// path to the toolchain crate root, relative to the top of the toolchain source
-	Toolchain_crate_root *string `android:"arch_variant"`
-	// path to the rest of the toolchain srcs, relative to the top of the toolchain source
-	Toolchain_srcs []string `android:"arch_variant"`
+	// path to the toolchain source, relative to the top of the toolchain source
+	Toolchain_src *string `android:"arch_variant"`
 }
 
 type toolchainLibraryDecorator struct {
@@ -89,20 +87,15 @@
 func rustSetToolchainSource(ctx android.LoadHookContext) {
 	if toolchainLib, ok := ctx.Module().(*Module).compiler.(*toolchainLibraryDecorator); ok {
 		prefix := "linux-x86/" + GetRustPrebuiltVersion(ctx)
-		versionedCrateRoot := path.Join(prefix, android.String(toolchainLib.Properties.Toolchain_crate_root))
-		versionedSrcs := make([]string, len(toolchainLib.Properties.Toolchain_srcs))
-		for i, src := range toolchainLib.Properties.Toolchain_srcs {
-			versionedSrcs[i] = path.Join(prefix, src)
-		}
+		newSrcs := []string{path.Join(prefix, android.String(toolchainLib.Properties.Toolchain_src))}
 
 		type props struct {
-			Crate_root *string
-			Srcs       []string
+			Srcs []string
 		}
 		p := &props{}
-		p.Crate_root = &versionedCrateRoot
-		p.Srcs = versionedSrcs
+		p.Srcs = newSrcs
 		ctx.AppendProperties(p)
+
 	} else {
 		ctx.ModuleErrorf("Called rustSetToolchainSource on a non-Rust Module.")
 	}