kbuild: prevent CC_FLAGS_LTO self-bloating on recursive rebuilds

CC_FLAGS_LTO gets initialized only via +=, never with := or =. When building with CONFIG_TRIM_UNUSED_KSYMS, Kbuild may perform several kernel rebuilds to satisfy symbol dependencies. In this case, value of CC_FLAGS_LTO is concatenated each time, which triggers a full rebuild. Initialize it with := to fix this.

Alexander Lobakin committed 5 years ago

Commit 2b868951 parent 112b6a81 file · +2 −2Browse files

Unified · Split

Makefile+2−2

@@ -895,10 +895,10 @@ endif · 894 unmodified lines
895	895
896	896	ifdef CONFIG_LTO_CLANG
897	897	ifdef CONFIG_LTO_CLANG_THIN
898		−CC_FLAGS_LTO += -flto=thin -fsplit-lto-unit
	898	+CC_FLAGS_LTO := -flto=thin -fsplit-lto-unit
899	899	KBUILD_LDFLAGS += --thinlto-cache-dir=$(extmod-prefix).thinlto-cache
900	900	else
901		−CC_FLAGS_LTO += -flto
	901	+CC_FLAGS_LTO := -flto
902	902	endif
903	903	CC_FLAGS_LTO += -fvisibility=hidden
904	904