build-macos: fix C++20 compatibility for Clang13.1

Fixes compilation on Clang13.1 by backporting some C++20
features that aren't available in Clang and fixing
the CMake config. Note that this doesn't yet properly package
the app nor does anything work at this point.

jthread, stop_token, and condition_variable_any impls taken from
josuttis/jthread and appleCompat.h taken from Citra and modified by me.

src/shader_recompiler/frontend/maxwell/decode.cpp

@@ -7,6 +7,9 @@
 #include <bit>
 #include <memory>
 
+#ifdef __APPLE__
+#include "common/apple_compat/appleCompat.h"
+#endif
 #include "common/common_types.h"
 #include "shader_recompiler/exception.h"
 #include "shader_recompiler/frontend/maxwell/decode.h"
@@ -63,9 +66,16 @@ constexpr std::array UNORDERED_ENCODINGS{
 
 constexpr auto SortedEncodings() {
     std::array encodings{UNORDERED_ENCODINGS};
+#ifdef __APPLE__
+    std::sort(encodings.begin(), encodings.end(),
+              [](const InstEncoding& lhs, const InstEncoding& rhs) {
+                  return std::popcount(lhs.mask_value.mask) > std::popcount(rhs.mask_value.mask);
+              });
+#else
     std::ranges::sort(encodings, [](const InstEncoding& lhs, const InstEncoding& rhs) {
         return std::popcount(lhs.mask_value.mask) > std::popcount(rhs.mask_value.mask);
     });
+#endif
     return encodings;
 }
 constexpr auto ENCODINGS{SortedEncodings()};