librdmacm/preload.c: fix duplicate symbol definitions on armhf

85f9747 introduces the preload of fcntl64 and it fails to build on armhf:

Assembler messages:
 Error: symbol `__fcntl_time64' is already defined
 Error: symbol `sendfile64' is already defined

On armhf, glibc defines both fcntl64 and fcntl as alias to __fcntl_time64.
As a consequence, in preload.c, 2 function definitions of fcntl64 and fcntl
are preprocessed to become the same function __fcntl_time64 definition,
that cause the double symbol error.

Only define and intercept these functions if they are not already defined.

This fixes the issue both for sendfile64 and fcntl64.

Signed-off-by: Hector Cao <hector.cao@canonical.com>

Author: hector-cao

librdmacm/preload.c

@@ -1185,7 +1185,7 @@ int fcntl(int socket, int cmd, ... /* arg */)
 	return ret;
 }
 
-#if RDMA_PRELOAD_WRAP_LFS64
+#if RDMA_PRELOAD_WRAP_LFS64 && !defined(fcntl64)
 int fcntl64(int socket, int cmd, ... /* arg */)
 {
 	va_list args;
@@ -1310,7 +1310,7 @@ ssize_t sendfile(int out_fd, int in_fd, off_t *offset, size_t count)
 	return ret;
 }
 
-#if RDMA_PRELOAD_WRAP_LFS64
+#if RDMA_PRELOAD_WRAP_LFS64 && !defined(sendfile64)
 ssize_t sendfile64(int out_fd, int in_fd, off64_t *offset64, size_t count)
 {
 	void *file_addr;