rust: Add support for bootstrap linker.

Adds the 'bootstrap' property to Rust modules to set the linker to the
bootstrap linker.

Bug: 194276829
Test: set bootstrap: true on module, checked .interp section on output.
Test: bootstrapped binary runs.
Change-Id: I459c8194902cfea3c44b060e70d28a43fcba3ade

rust/builder.go

@@ -220,6 +220,15 @@ func transformSrctoCrate(ctx ModuleContext, main android.Path, deps PathDeps, fl
 	linkFlags = append(linkFlags, flags.GlobalLinkFlags...)
 	linkFlags = append(linkFlags, flags.LinkFlags...)
 
+	// Check if this module needs to use the bootstrap linker
+	if ctx.RustModule().Bootstrap() && !ctx.RustModule().InRecovery() && !ctx.RustModule().InRamdisk() && !ctx.RustModule().InVendorRamdisk() {
+		dynamicLinker := "-Wl,-dynamic-linker,/system/bin/bootstrap/linker"
+		if ctx.toolchain().Is64Bit() {
+			dynamicLinker += "64"
+		}
+		linkFlags = append(linkFlags, dynamicLinker)
+	}
+
 	libFlags := makeLibFlags(deps)
 
 	// Collect dependencies