Don't require ABI tools if not checking the ABI

Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>

scripts/abi_check.py

@@ -480,7 +480,8 @@ class AbiChecker:
         """Generate a report of ABI differences
         between self.old_rev and self.new_rev."""
         self.check_repo_path()
-        self.check_abi_tools_are_installed()
+        if self.check_api or self.check_abi:
+            self.check_abi_tools_are_installed()
         self._get_abi_dump_for_ref(self.old_version)
         self._get_abi_dump_for_ref(self.new_version)
         return self.get_abi_compatibility_report()