AST: unblock linux build by providing explicit constructor

Author: nkcsgexi

lib/AST/Decl.cpp

@@ -490,7 +490,7 @@ const Decl::CachedExternalSourceLocs *Decl::calculateSerializedLocs() const {
   auto *File = cast<FileUnit>(getDeclContext()->getModuleScopeContext());
   auto Locs = File->getBasicLocsForDecl(this);
   if (!Locs.hasValue()) {
-    static const Decl::CachedExternalSourceLocs NullLocs;
+    static const Decl::CachedExternalSourceLocs NullLocs{};
     return &NullLocs;
   }
   auto *Result = getASTContext().Allocate<Decl::CachedExternalSourceLocs>();

utils/gyb_sourcekit_support/UIDs.py

@@ -174,6 +174,7 @@ def __init__(self, internal_name, external_name):
     KEY('VFSName', 'key.vfs.name'),
     KEY('VFSOptions', 'key.vfs.options'),
     KEY('Files', 'key.files'),
+    KEY('IgnoreSourceInfoFile', 'key.ignore_source_info_file'),
 ]