cmake: Add cmake/introspection.cmake file

CMakeLists.txt

@@ -58,6 +58,8 @@ else()
 endif()
 set(CMAKE_POSITION_INDEPENDENT_CODE ON)
 
+include(cmake/introspection.cmake)
+
 add_subdirectory(src)
 
 message("\n")

cmake/bitcoin-config.h.in

@@ -42,4 +42,8 @@
 /* Define to the version of this package. */
 #define PACKAGE_VERSION "@PROJECT_VERSION@"
 
+/* Define WORDS_BIGENDIAN to 1 if your processor stores words with the most
+   significant byte first (like Motorola and SPARC, unlike Intel). */
+#cmakedefine WORDS_BIGENDIAN 1
+
 #endif //BITCOIN_CONFIG_H

cmake/introspection.cmake

@@ -0,0 +1,7 @@
+# Copyright (c) 2023 The Bitcoin Core developers
+# Distributed under the MIT software license, see the accompanying
+# file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+include(TestBigEndian)
+
+test_big_endian(WORDS_BIGENDIAN)