private List<Long> getUnresolvedExternalFunctionIds() {
			List<Long> symbolIds = new ArrayList<>();
			ExternalManager externalManager = program.getExternalManager();
			Library library = externalManager.getExternalLibrary(Library.UNKNOWN);
			if (library != null) {
				for (Symbol s : program.getSymbolTable().getSymbols(library)) {
					if (s.getSymbolType() == SymbolType.FUNCTION &&
						s.getSource() != SourceType.DEFAULT) {
						symbolIds.add(s.getID());
					}
				}
			}
			return symbolIds;
		}
Returns a list of all external functions under the EXTERNAL/UNKNOWN library.

@return list of func ids that need to be fixed
Ghidra/Features/Base/src/main/java/ghidra/program/util/ExternalSymbolResolver.java