The ninja 'iwyu' target does not depend nor generates
compile_commands_wo_subprojects/compile_commands.json. Hence iwyu
would fail if the database is not yet generated or run with an
outdated compile_commands.json.

Instead of iwyu being added to STATIC_ANALYSIS_NINJA_TARGETS, we now
have the static-analysis make target depend on iwyu. This ensures that
compile_commands_wo_subprojects/compile_commands.json is generated or
updated (if required) before iwyu is run.p