Suppress -Wincompatible-pointer-types when needed

LLVM Clang 22+ treats -Wincompatible-pointer-types as an error
by default, which breaks compilation of mini_racer_extension.c
due to the unsigned long vs uint64_t mismatch in the bigint
serialization code.

Add -Wno-incompatible-pointer-types to CFLAGS when the compiler
rejects an unsigned long to uint64_t pointer conversion, as a
workaround until the type mismatch is properly fixed in the
extension source.

Ref: #359
Ref: #361

Author: knu

ext/mini_racer_extension/extconf.rb

@@ -32,6 +32,17 @@
 
 $CXXFLAGS += " -Wno-reserved-user-defined-literal" if IS_DARWIN
 
+# LLVM Clang 22+ treats -Wincompatible-pointer-types as an error by default;
+# suppress it until the `unsigned long` vs `uint64_t` mismatch in the extension
+# is properly fixed.
+unless try_compile(<<~'C', '-Wincompatible-pointer-types')
+  #include <stdint.h>
+  void f(const uint64_t *p) { (void)p; }
+  void g(void) { unsigned long a[1]; f(a); }
+C
+  $CFLAGS += " -Wno-incompatible-pointer-types"
+end
+
 if IS_DARWIN
   $LDFLAGS.insert(0, " -stdlib=libc++ ")
 else