Fix u-boot build for gcc-5.1

Test: TOOLCHAIN=gcc-5.1 make u-boot
Change-Id: Ic3bdc7b9ffa431ae08d49cc4fb01d9d94a5ab6cf
diff --git a/Makefile b/Makefile
index f9895ad..47ff4cb 100644
--- a/Makefile
+++ b/Makefile
@@ -272,9 +272,9 @@
 $(warning "gcc below 6.0 is not supported by u-boot, switching to 9.2")
 UBOOT_TOOLCHAIN_BIN := $(TOOLCHAIN_GCC_92)/bin
 UBOOT_TARGET = $(TARGET_GCC_92)
-UBOOT_CC := $(TOOLCHAIN_BIN)/$(TARGET)-gcc
-UBOOT_LD := $(TOOLCHAIN_BIN)/$(TARGET)-ld
-UBOOT_GCC_TOOLCHAIN_BIN := $(TOOLCHAIN_BIN)
+UBOOT_CC := $(UBOOT_TOOLCHAIN_BIN)/$(UBOOT_TARGET)-gcc
+UBOOT_LD := $(UBOOT_TOOLCHAIN_BIN)/$(UBOOT_TARGET)-ld
+UBOOT_GCC_TOOLCHAIN_BIN := $(UBOOT_TOOLCHAIN_BIN)
 else
 UBOOT_TOOLCHAIN_BIN := $(TOOLCHAIN_BIN)
 UBOOT_TARGET = $(TARGET)