populate_sdk_ext: Exclude BBTASKDEPDATA from task signature

Otherwise the task hash changes between server and worker context
leading to changing task checksums. The dependency data here is
tracked by other pieces of the signature.

(From OE-Core rev: 1962571a7358fb9c9af2d6cfd1a01673b0d18193)

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/classes/populate_sdk_ext.bbclass

@@ -51,6 +51,8 @@ def get_sdk_install_targets(d):
 
     return sdk_install_targets
 
+get_sdk_install_targets[vardepsexclude] = "BB_TASKDEPDATA"
+
 OE_INIT_ENV_SCRIPT ?= "oe-init-build-env"
 
 # The files from COREBASE that you want preserved in the COREBASE copied