$OpenBSD: patch-config_makefiles_rust_mk,v 1.6 2021/01/26 15:52:58 landry Exp $

use lto=thin to reduce memory pressure when building gkrust
https://bugzilla.mozilla.org/show_bug.cgi?id=1644409
https://bugzilla.mozilla.org/show_bug.cgi?id=1640982

Index: config/makefiles/rust.mk
--- a/config/makefiles/rust.mk.orig
+++ a/config/makefiles/rust.mk
@@ -70,7 +70,8 @@ ifndef MOZ_DEBUG_RUST
 # gkrust_gtest. And not when doing cross-language LTO.
 ifndef MOZ_LTO_RUST_CROSS
 ifeq (,$(findstring gkrust_gtest,$(RUST_LIBRARY_FILE)))
-cargo_rustc_flags += -Clto
+cargo_rustc_flags += -Clto=thin
+export CARGO_PROFILE_RELEASE_LTO=thin
 endif
 # We need -Cembed-bitcode=yes for all crates when using -Clto.
 RUSTFLAGS += -Cembed-bitcode=yes