build_package: checkout SCMI library from settings

The tools-non-public contains a reference to the correct
commit for the SCMI library to be used for testing.
This patch makes sure that the above reference is also used
in this test instance.

Change-Id: If6cb79843d06d0393e2edb7edadfda90491ef797
Signed-off-by: Nicola Mazzucato <nicola.mazzucato@arm.com>
diff --git a/script/build_package.sh b/script/build_package.sh
index 75d3024..a99adec 100755
--- a/script/build_package.sh
+++ b/script/build_package.sh
@@ -617,7 +617,10 @@
 
 	git submodule update
 
+	lib_commit=$(grep "'scmi_lib_commit'" run_tests/settings.py | cut -d':' -f 2 | tr -d "'")
+
 	cd "scmi"
+	git checkout $lib_commit
 
 	git show --quiet --no-color | sed 's/^/  > /g'
 }