build_package.sh: Retry SPM submodule operations

These fail frequently for LTS builds.

Signed-off-by: Paul Sokolovsky <paul.sokolovsky@linaro.org>
Change-Id: I4accef70afc8fb90c7cf0d04e8e8208e572662bf
(cherry picked from commit be6510c3a1fbb6a1e494490218c5df3ed37965a7)
1 file changed