diff --git a/toolchain.inc b/toolchain.inc
index de504711a7..e089f2ee5f 100644
--- a/toolchain.inc
+++ b/toolchain.inc
@@ -106,9 +106,9 @@ CFLAGS_$(1) = $$(CFLAGS_common) $$(CFLAGS_$(2))
 CPPFLAGS_$(1) = $$(CPPFLAGS_common) $$(CPPFLAGS_$(2))
 COMPILER_RT_FLAGS_$(1) :=
 ifeq ($(CONFIG_COMPILER_LLVM_CLANG),y)
-COMPILER_RT_$(1) = $(shell $(CC_$(2)) $(CFLAGS_$(2)) -print-librt-file-name 2>/dev/null)
+COMPILER_RT_$(1) := $(shell $(CC_$(2)) $(CFLAGS_$(2)) -print-librt-file-name 2>/dev/null)
 else
-COMPILER_RT_$(1) = $(wildcard $(shell $(CC_$(2)) $(CFLAGS_$(2)) -print-libgcc-file-name))
+COMPILER_RT_$(1) := $(wildcard $(shell $(CC_$(2)) $(CFLAGS_$(2)) -print-libgcc-file-name))
 ifeq ($(2),x86_32)
 COMPILER_RT_FLAGS_$(1) := --wrap __divdi3 --wrap __udivdi3 --wrap __moddi3 --wrap __umoddi3
 endif