meta-toolchain-osmo: Attempt to fix hash data issue

Exclude DATETIME from the variables to fix errors like:

ERROR: meta-toolchain-osmo-1.0-r7 do_populate_sdk: Taskhash mismatch 0fb3116488402f87d1e4d637af229664 verses 6dda5ee949e484709fbac4a097018fc2 for meta-telephony/recipes-osmocom/meta/meta-toolchain-osmo.bb.do_populate_sdk
diff --git a/recipes-osmocom/meta/meta-toolchain-osmo.bb b/recipes-osmocom/meta/meta-toolchain-osmo.bb
index 6755fb6..a2fb793 100644
--- a/recipes-osmocom/meta/meta-toolchain-osmo.bb
+++ b/recipes-osmocom/meta/meta-toolchain-osmo.bb
@@ -2,6 +2,7 @@
 TOOLCHAIN_TARGET_TASK = "${TOOLCHAIN_TARGET_OSMOTASK}"
 TOOLCHAIN_OUTPUT_BASENAME = "${SDK_NAME}-toolchain-osmo-${DISTRO_VERSION}"
 TOOLCHAIN_OUTPUTNAME = "${TOOLCHAIN_OUTPUT_BASENAME}-${DATETIME}"
+TOOLCHAIN_OUTPUTNAME[vardepsexclude] = "DATETIME"
 PROVIDES = "meta-toolchain-sdk"
 require recipes-core/meta/meta-toolchain.bb