Remove unnecessary `android:"path"` tags in rust

Custom_bindgen is handled by adding a relevant dependency tag.
Flags and Ld_flags are not paths/references to other modules.

Test: go test soong tests
Change-Id: Ic6a69521102318b3b9f29b59560bcefbc9aff8fa

rust/bindgen.go

@@ -79,7 +79,7 @@ type BindgenProperties struct {
 	// binary must expect arguments in a similar fashion to bindgen, e.g.
 	//
 	// "my_bindgen [flags] wrapper_header.h -o [output_path] -- [clang flags]"
-	Custom_bindgen string `android:"path"`
+	Custom_bindgen string
 }
 
 type bindgenDecorator struct {

rust/compiler.go

@@ -77,10 +77,10 @@ type BaseCompilerProperties struct {
 	Lints *string
 
 	// flags to pass to rustc. To enable configuration options or features, use the "cfgs" or "features" properties.
-	Flags []string `android:"path,arch_variant"`
+	Flags []string `android:"arch_variant"`
 
 	// flags to pass to the linker
-	Ld_flags []string `android:"path,arch_variant"`
+	Ld_flags []string `android:"arch_variant"`
 
 	// list of rust rlib crate dependencies
 	Rlibs []string `android:"arch_variant"`