toolchain/external: ignore missing hash for custom downloaded toolchain

We will *always* be missing a hash file for custom external toolchains
that are downloaded.

So, just ignore that failure.

Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Signed-off-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>
Cc: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Cc: Gustavo Zacarias <gustavo@zacarias.com.ar>
Acked-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>
Acked-by: Gustavo Zacarias <gustavo@zacarias.com.ar>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>

toolchain/toolchain-external/toolchain-external.mk

@@ -400,6 +400,8 @@ else
 # Custom toolchain
 TOOLCHAIN_EXTERNAL_SITE = $(dir $(call qstrip,$(BR2_TOOLCHAIN_EXTERNAL_URL)))
 TOOLCHAIN_EXTERNAL_SOURCE = $(notdir $(call qstrip,$(BR2_TOOLCHAIN_EXTERNAL_URL)))
+# We can't check hashes for custom downloaded toolchains
+BR_NO_CHECK_HASH_FOR += $(TOOLCHAIN_EXTERNAL_SOURCE)
 endif
 
 # In fact, we don't need to download the toolchain, since it is already