Merge bitcoin/bitcoin#24337: build: Do not define PROVIDE_FUZZ_MAIN_FUNCTION macro unconditionally

c9c4e6c build: Do not define `PROVIDE_FUZZ_MAIN_FUNCTION` macro unconditionally (Hennadii Stepanov)

Pull request description:

  No need to define the `PROVIDE_FUZZ_MAIN_FUNCTION` macro when the build system has been configured with the `--disable-fuzz-binary` option.

  See bitcoin/bitcoin#24336 (review).

ACKs for top commit:
  MarcoFalke:
    Approach ACK c9c4e6c did not review or test 🐤
  fanquake:
    ACK c9c4e6c Checked that `PROVIDE_FUZZ_MAIN_FUNCTION` isn't defined when configuring with `--disable-fuzz-binary`.

Tree-SHA512: 54fbf02ba9f5ecc61b176b8ea7d05e308788d4de3f97ed40913e731300d9dc0edfdfcbf8e0a6e74cf1b2e2ae63f6208a34e03b9c8d203d070c457c4a7d9b5f2c

Author: fanquake

configure.ac

@@ -1300,21 +1300,6 @@ if test "$enable_fuzz" = "yes"; then
   enable_fuzz_binary=yes
 
   AX_CHECK_PREPROC_FLAG([-DABORT_ON_FAILED_ASSUME], [DEBUG_CPPFLAGS="$DEBUG_CPPFLAGS -DABORT_ON_FAILED_ASSUME"], [], [$CXXFLAG_WERROR])
-
-  AC_MSG_CHECKING([whether main function is needed for fuzz binary])
-  AX_CHECK_LINK_FLAG(
-    [-fsanitize=$use_sanitizers],
-    [AC_MSG_RESULT([no])],
-    [AC_MSG_RESULT([yes]); CORE_CPPFLAGS="$CORE_CPPFLAGS -DPROVIDE_FUZZ_MAIN_FUNCTION"],
-    [],
-    [AC_LANG_PROGRAM([[
-      #include <cstdint>
-      #include <cstddef>
-      extern "C" int LLVMFuzzerTestOneInput(const uint8_t *data, size_t size) { return 0; }
-      /* comment to remove the main function ...
-     ]],[[
-      */ int not_main() {
-     ]])])
 else
   BITCOIN_QT_INIT
 
@@ -1328,8 +1313,25 @@ else
     QT_DBUS_INCLUDES=SUPPRESS_WARNINGS($QT_DBUS_INCLUDES)
     QT_TEST_INCLUDES=SUPPRESS_WARNINGS($QT_TEST_INCLUDES)
   fi
+fi
+
+if test "$enable_fuzz_binary" = "yes"; then
+  AC_MSG_CHECKING([whether main function is needed for fuzz binary])
+  AX_CHECK_LINK_FLAG(
+    [],
+    [AC_MSG_RESULT([no])],
+    [AC_MSG_RESULT([yes]); CORE_CPPFLAGS="$CORE_CPPFLAGS -DPROVIDE_FUZZ_MAIN_FUNCTION"],
+    [$SANITIZER_LDFLAGS],
+    [AC_LANG_PROGRAM([[
+      #include <cstdint>
+      #include <cstddef>
+      extern "C" int LLVMFuzzerTestOneInput(const uint8_t* data, size_t size) { return 0; }
+      /* comment to remove the main function ...
+     ]],[[
+      */ int not_main() {
+     ]])])
 
-  CORE_CPPFLAGS="$CORE_CPPFLAGS -DPROVIDE_FUZZ_MAIN_FUNCTION"
+  CHECK_RUNTIME_LIB
 fi
 
 if test "$enable_wallet" != "no"; then
@@ -1819,10 +1821,6 @@ if test "$build_bitcoin_wallet$build_bitcoin_cli$build_bitcoin_tx$build_bitcoin_
   AC_MSG_ERROR([No targets! Please specify at least one of: --with-utils --with-libs --with-daemon --with-gui --enable-bench or --enable-tests])
 fi
 
-if test "$enable_fuzz_binary" = "yes"; then
-  CHECK_RUNTIME_LIB
-fi
-
 AM_CONDITIONAL([TARGET_DARWIN], [test "$TARGET_OS" = "darwin"])
 AM_CONDITIONAL([BUILD_DARWIN], [test "$BUILD_OS" = "darwin"])
 AM_CONDITIONAL([TARGET_LINUX], [test "$TARGET_OS" = "linux"])