Add option to skip identifiers in ABI checks

By default abi-compliance-checker will check the entire ABI/API.
There are internal identifiers that we do not promise compatibility
for, so we want the ability to skip them when checking the ABI/API.

scripts/abi_check.py

@@ -29,7 +29,7 @@ class AbiChecker(object):
     """API and ABI checker."""
 
     def __init__(self, report_dir, old_repo, old_rev, new_repo, new_rev,
-                 keep_all_reports):
+                 keep_all_reports, skip_file=None):
         """Instantiate the API/ABI checker.
 
         report_dir: directory for output files
@@ -38,6 +38,7 @@ class AbiChecker(object):
         new_repo: repository for git revision to check
         new_rev: git revision to check
         keep_all_reports: if false, delete old reports
+        skip_file: path to file containing symbols and types to skip
         """
         self.repo_path = "."
         self.log = None
@@ -49,6 +50,7 @@ class AbiChecker(object):
         self.old_rev = old_rev
         self.new_repo = new_repo
         self.new_rev = new_rev
+        self.skip_file = skip_file
         self.mbedtls_modules = ["libmbedcrypto", "libmbedtls", "libmbedx509"]
         self.old_dumps = {}
         self.new_dumps = {}
@@ -216,6 +218,9 @@ class AbiChecker(object):
                 "-strict",
                 "-report-path", output_path
             ]
+            if self.skip_file:
+                abi_compliance_command += ["-skip-symbols", self.skip_file,
+                                           "-skip-types", self.skip_file]
             abi_compliance_process = subprocess.Popen(
                 abi_compliance_command,
                 stdout=subprocess.PIPE,
@@ -292,6 +297,10 @@ def run_main():
                   "Can include repository before revision"),
             required=True, nargs="+"
         )
+        parser.add_argument(
+            "-s", "--skip-file", type=str,
+            help="path to file containing symbols and types to skip"
+        )
         abi_args = parser.parse_args()
         if len(abi_args.old_rev) == 1:
             old_repo = None
@@ -311,7 +320,8 @@ def run_main():
             raise Exception("Too many arguments passed for new version")
         abi_check = AbiChecker(
             abi_args.report_dir, old_repo, old_rev,
-            new_repo, new_rev, abi_args.keep_all_reports
+            new_repo, new_rev, abi_args.keep_all_reports,
+            abi_args.skip_file
         )
         return_code = abi_check.check_for_abi_changes()
         sys.exit(return_code)