meson: drop dladdr check on win32

since !17208 (merged) there are 2 paths for disk_cache_get_function_identifier on mingw: DETECT_OS_WINDOWS or HAVE_DLADDR (if dlfcn shims is present)

../src/util/disk_cache_os.c:47:1: error: redefinition of 'disk_cache_get_function_identifier'
   47 | disk_cache_get_function_identifier(void *ptr, struct mesa_sha1 *ctx)
      | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
In file included from ../src/util/disk_cache_os.c:36:
../src/util/disk_cache.h:121:1: note: previous definition of 'disk_cache_get_function_identifier' with type '_Bool(void *, struct _SHA1_CTX *)'
  121 | disk_cache_get_function_identifier(void *ptr, struct mesa_sha1 *ctx)

here we disable the dladdr path from meson for consistency with msvc

fixes: 2dcbe872

cc @jenatali