This change avoids having to run the genseccomp.py script every time a
policy file is edited, and instead generates these files at
compile-time.
Bug: None
Test: m
Test: find out/soong/ -name x86_64_global_policy.cpp # Shows files
Test: generated policies are equivalent to original policies
Change-Id: I12461fe0c5fb02c008c1b2503fbb994b8aa2f56b
