Xcode/clang no longer compiling C++14 code after updating Xcode: "no member named make_shared"

I am no longer able to build my C++ project after coming back to it after a while (I've since updated macOS and Xcode), either from Xcode or by calling clang on the command line. I am getting an error on every use of std::shared_ptr::make_shared in my code. I want to emphasize this used to compile and run fine and I don't understand what has changed. Perhaps updating xcode broke my toolchain somehow.

I have reproduced the problem in some very trivial code that I believe should compile fine:

#include <string>
#include <memory>

class test_c {
    private:
        std::string str_;
    
    public:
        test_c(std::string str__) : str_(str__) { }
};

std::string test_s = "test";
auto test = std::shared_ptr<test_c>::make_shared(test_s);

The errors look like this:

$ clang -std=c++14 test.cpp
test.cpp:10:38: error: no member named 'make_shared' in 'std::__1::shared_ptr<test_c>'
auto test = std::shared_ptr<test_c>::make_shared(test_s);
            ~~~~~~~~~~~~~~~~~~~~~~~~~^
1 error generated.