Merge bitcoin/bitcoin#27057: build: set boost cppflags with --enable-fuzz

b03a982 build: set boost cppflags with --enable-fuzz (fanquake)

Pull request description:

  Even though all other targets are disabled, we still need Boost CPPFLAGS (`use_boost`) to compile. This currently works everywhere, except on arm macOS (where the include path is non-standard), because generally, the Boost include path is generic, i.e `/usr/include`.

ACKs for top commit:
  hebasto:
    ACK b03a982

Tree-SHA512: 7544a903ce641fd4b994ae51423a7007de85628ae29be36362a5cbdd62f9b16ac0a62e9edadaaa998ad4c1e82c0fde0d8c53aba41f94ad30ffa9f10ba0984521

Author: fanquake

configure.ac

@@ -1451,7 +1451,7 @@ if test "$use_natpmp" != "no"; then
   CPPFLAGS="$TEMP_CPPFLAGS"
 fi
 
-if test "$build_bitcoin_wallet$build_bitcoin_cli$build_bitcoin_tx$build_bitcoin_util$build_bitcoind$bitcoin_enable_qt$use_tests$use_bench" = "nononononononono"; then
+if test "$build_bitcoin_wallet$build_bitcoin_cli$build_bitcoin_tx$build_bitcoin_util$build_bitcoind$bitcoin_enable_qt$use_tests$use_bench$enable_fuzz_binary" = "nonononononononono"; then
   use_boost=no
 else
   use_boost=yes