apacheGH-43688: [C++] Prevent Snappy from disabling RTTI when bundled

cpp/cmake_modules/ThirdpartyToolchain.cmake

@@ -1353,26 +1353,9 @@ macro(build_snappy)
   set(SNAPPY_CMAKE_ARGS
       ${EP_COMMON_CMAKE_ARGS} -DSNAPPY_BUILD_TESTS=OFF -DSNAPPY_BUILD_BENCHMARKS=OFF
       "-DCMAKE_INSTALL_PREFIX=${SNAPPY_PREFIX}")
-  # Snappy unconditionally enables -Werror when building with clang this can lead
-  # to build failures by way of new compiler warnings. This adds a flag to disable
-  # Werror to the very end of the invocation to override the snappy internal setting.
-  if(CMAKE_CXX_COMPILER_ID MATCHES "Clang")
-    foreach(CONFIG DEBUG MINSIZEREL RELEASE RELWITHDEBINFO)
-      list(APPEND
-           SNAPPY_CMAKE_ARGS
-           "-DCMAKE_CXX_FLAGS_${UPPERCASE_BUILD_TYPE}=${EP_CXX_FLAGS_${CONFIG}} -Wno-error"
-      )
-    endforeach()
-  endif()
-
-  if(APPLE AND CMAKE_HOST_SYSTEM_VERSION VERSION_LESS 20)
-    # On macOS 10.13 we need to explicitly add <functional> to avoid a missing include error
-    # This can be removed once CRAN no longer checks on macOS 10.13
-    find_program(PATCH patch REQUIRED)
-    set(SNAPPY_PATCH_COMMAND ${PATCH} -p1 -i ${CMAKE_CURRENT_LIST_DIR}/snappy.diff)
-  else()
-    set(SNAPPY_PATCH_COMMAND)
-  endif()
+  # See comments in snappy.diff.
+  find_program(PATCH patch REQUIRED)
+  set(SNAPPY_PATCH_COMMAND ${PATCH} -p1 -i ${CMAKE_CURRENT_LIST_DIR}/snappy.diff)
 
   if(CMAKE_SYSTEM_NAME STREQUAL "Emscripten")
     # ignore linker flag errors, as Snappy sets

cpp/cmake_modules/snappy.diff

@@ -14,9 +14,41 @@
 # KIND, either express or implied.  See the License for the
 # specific language governing permissions and limitations
 # under the License.
-#
-# https://github.com/google/snappy/pull/172
 
+# 1. Snappy unconditionally enables -Werror when building with clang this can lead
+# to build failures by way of new compiler warnings. This adds a flag to disable
+# -Werror to the very end of the invocation to override the snappy internal setting.
+# 2. Snappy unconditionally disables RTTI, which is incompatible with some other
+# build settings (https://github.com/apache/arrow/issues/43688).
+# 3. On macOS 10.13 we need to explicitly add <functional> to avoid a missing
+# include error. This can be removed once CRAN no longer checks on macOS 10.13
+# (https://github.com/google/snappy/pull/172).
+
+diff --git a/CMakeLists.txt b/CMakeLists.txt
+index c3062e2..21b49a7 100644
+--- a/CMakeLists.txt
++++ b/CMakeLists.txt
+@@ -66,20 +66,9 @@ else(CMAKE_CXX_COMPILER_ID STREQUAL "MSVC")
+     set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Wextra")
+   endif(NOT CMAKE_CXX_FLAGS MATCHES "-Wextra")
+
+-  # Use -Werror for clang only.
+-  if(CMAKE_CXX_COMPILER_ID MATCHES "Clang")
+-    if(NOT CMAKE_CXX_FLAGS MATCHES "-Werror")
+-      set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Werror")
+-    endif(NOT CMAKE_CXX_FLAGS MATCHES "-Werror")
+-  endif(CMAKE_CXX_COMPILER_ID MATCHES "Clang")
+-
+   # Disable C++ exceptions.
+   string(REGEX REPLACE "-fexceptions" "" CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS}")
+   set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -fno-exceptions")
+-
+-  # Disable RTTI.
+-  string(REGEX REPLACE "-frtti" "" CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS}")
+-  set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -fno-rtti")
+ endif(CMAKE_CXX_COMPILER_ID STREQUAL "MSVC")
+
+ # BUILD_SHARED_LIBS is a standard CMake variable, but we declare it here to make
 diff --git a/snappy.cc b/snappy.cc
 index d414718..5b0d0d6 100644
 --- a/snappy.cc