Patch abseil-cpp to ignore deprecated errors in new Xcode. (#12498)

cmake/external/abseil-cpp.cmake

@@ -14,6 +14,7 @@
 
 include(ExternalProject)
 
+# Note: When updating to 20230802.0 or later, remove the PATCH_COMMAND below.
 set(version 20220623.0)
 
 ExternalProject_Add(
@@ -31,4 +32,6 @@ ExternalProject_Add(
   INSTALL_COMMAND ""
   TEST_COMMAND ""
   HTTP_HEADER "${EXTERNAL_PROJECT_HTTP_HEADER}"
+
+  PATCH_COMMAND patch -Np1 -i ${CMAKE_CURRENT_LIST_DIR}/abseil-cpp.patch.txt
 )

cmake/external/abseil-cpp.patch.txt

@@ -0,0 +1,27 @@
+diff --git a/absl/meta/type_traits.h b/absl/meta/type_traits.h
+index d886cb30..c2a2d15e 100644
+--- a/absl/meta/type_traits.h
++++ b/absl/meta/type_traits.h
+@@ -35,6 +35,12 @@
+ #ifndef ABSL_META_TYPE_TRAITS_H_
+ #define ABSL_META_TYPE_TRAITS_H_
+
++// Added by firebase-ios-sdk/cmake/external/abseil-cpp.patch.txt
++#if __clang__
++#pragma clang diagnostic push
++#pragma clang diagnostic ignored "-Wdeprecated"
++#endif  // __clang__
++
+ #include <cstddef>
+ #include <functional>
+ #include <type_traits>
+@@ -794,4 +800,9 @@ using swap_internal::StdSwapIsUnconstrained;
+ ABSL_NAMESPACE_END
+ }  // namespace absl
+
++// Added by firebase-ios-sdk/cmake/external/abseil-cpp.patch.txt
++#if __clang__
++#pragma clang diagnostic pop
++#endif  // __clang__
++
+ #endif  // ABSL_META_TYPE_TRAITS_H_