introspector: force header-only targets (#414)

Adds a new option from fuzz introspector that makes it possible to
select benchmarks only if they are determined to be declared in a header
file. This is part of a wider effort in more accurately descriping the
header files to include in a given harness.

Ref: ossf/fuzz-introspector#1624
Ref: ossf/fuzz-introspector#1641

Signed-off-by: David Korczynski <david@adalogics.com>

data_prep/introspector.py

@@ -44,6 +44,8 @@
     int(os.getenv('OSS_FUZZ_AVOID_STATIC_FUNCTIONS', '1')))
 ORACLE_ONLY_REFERENCED_FUNCTIONS = bool(
     int(os.getenv('OSS_FUZZ_ONLY_REFERENCED_FUNCTIONS', '0')))
+ORACLE_ONLY_FUNCTIONS_WITH_HEADER_DECLARATIONS = bool(
+    int(os.getenv('OSS_FUZZ_ONLY_FUNCS_WITH_HEADER_DECLARATION', '1')))
 
 DEFAULT_INTROSPECTOR_ENDPOINT = 'https://introspector.oss-fuzz.com/api'
 INTROSPECTOR_ENDPOINT = ''
@@ -192,9 +194,14 @@ def query_introspector_oracle(project: str, oracle_api: str) -> list[dict]:
   """Queries a fuzz target oracle API from Fuzz Introspector."""
   resp = _query_introspector(
       oracle_api, {
-          'project': project,
-          'exclude-static-functions': ORACLE_AVOID_STATIC_FUNCTIONS,
-          'only-referenced-functions': ORACLE_ONLY_REFERENCED_FUNCTIONS,
+          'project':
+              project,
+          'exclude-static-functions':
+              ORACLE_AVOID_STATIC_FUNCTIONS,
+          'only-referenced-functions':
+              ORACLE_ONLY_REFERENCED_FUNCTIONS,
+          'only-with-header-file-declaration':
+              ORACLE_ONLY_FUNCTIONS_WITH_HEADER_DECLARATIONS,
       })
   return _get_data(resp, 'functions', [])