rust: Allow no_stdlibs per-target variants.

stdlibs can be set per-target, it makes to sense to allow no_stdlibs to
be set per-target as well.

Bug: 310924208
Test: Android.bp with per-target no_stdlibs builds.
Change-Id: I1c3a458a849367d2c363bd5f65af77b8cce8c0e0
diff --git a/rust/compiler.go b/rust/compiler.go
index b3f574d..4c7961d 100644
--- a/rust/compiler.go
+++ b/rust/compiler.go
@@ -160,7 +160,7 @@
 	Relative_install_path *string `android:"arch_variant"`
 
 	// whether to suppress inclusion of standard crates - defaults to false
-	No_stdlibs *bool
+	No_stdlibs *bool `android:"arch_variant"`
 
 	// Change the rustlibs linkage to select rlib linkage by default for device targets.
 	// Also link libstd as an rlib as well on device targets.