diff -up firefox-68.0/config/makefiles/rust.mk.old firefox-68.0/config/makefiles/rust.mk
--- firefox-68.0/config/makefiles/rust.mk.old	2019-06-05 10:33:34.290128660 +0200
+++ firefox-68.0/config/makefiles/rust.mk	2019-06-05 10:33:59.835052814 +0200
@@ -47,7 +47,7 @@ cargo_rustc_flags = $(CARGO_RUSTCFLAGS)
 ifndef DEVELOPER_OPTIONS
 ifndef MOZ_DEBUG_RUST
 # Enable link-time optimization for release builds.
-cargo_rustc_flags += -C lto
+#cargo_rustc_flags += -C lto
 endif
 endif