Remove USE_CLANG_LLD[=false]

This should always be true now. It will be a change for side branches
(build_tools, etc) that weren't setting UseClangLld in the
soong.variables file.

Test: treehugger
Change-Id: I9fd6157fda630bf8bb939677dbcb026f02685f19
diff --git a/cc/lto.go b/cc/lto.go
index fd2a869..52b9a34 100644
--- a/cc/lto.go
+++ b/cc/lto.go
@@ -76,7 +76,7 @@
 	if lto.Properties.Use_clang_lld != nil {
 		return Bool(lto.Properties.Use_clang_lld)
 	}
-	return ctx.Config().UseClangLld()
+	return true
 }
 
 func (lto *lto) flags(ctx BaseModuleContext, flags Flags) Flags {