samples, bpf: Suppress compiler warning

samples, bpf: Suppress compiler warning

While cross compiling on ARM32 , the casting from pointer to __u64 will
cause warnings:

samples/bpf/task_fd_query_user.c: In function 'main':
samples/bpf/task_fd_query_user.c:399:23: warning: cast from pointer to integer of different size [-Wpointer-to-int-cast]
399 | uprobe_file_offset = (__u64)main - (__u64)&__executable_start;
| ^
samples/bpf/task_fd_query_user.c:399:37: warning: cast from pointer to integer of different size [-Wpointer-to-int-cast]
399 | uprobe_file_offset = (__u64)main - (__u64)&__executable_start;

Workaround this by using "unsigned long" to adapt to different ARCHs.

Signed-off-by: Hailong Liu <liu.hailong6@zte.com.cn>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20210511140429.89426-1-liuhailongg6@163.com