tools lib bpf: Use official ELF e_machine value

New LLVM will issue newly assigned EM_BPF machine code. The new code
will be propagated to glibc and libelf.

This patch introduces the new machine code to libbpf.

Signed-off-by: Wang Nan <[e-mail]>
Acked-by: Alexei Starovoitov <[e-mail]>
Cc: Zefan Li <[e-mail]>
Cc: [e-mail]
Link: http://lkml.kernel.org/r/[e-mail]
Signed-off-by: Arnaldo Carvalho de Melo <[e-mail]>

tools/lib/bpf/libbpf.c

···
 #include "libbpf.h"
 #include "bpf.h"
 
+#ifndef EM_BPF
+#define EM_BPF 247
+#endif
+
 #define __printf(a, b)	__attribute__((format(printf, a, b)))
 
 __printf(1, 2)
···
 	}
 	ep = &obj->efile.ehdr;
 
-	if ((ep->e_type != ET_REL) || (ep->e_machine != 0)) {
+	/* Old LLVM set e_machine to EM_NONE */
+	if ((ep->e_type != ET_REL) || (ep->e_machine && (ep->e_machine != EM_BPF))) {
 		pr_warning("%s is not an eBPF object file\n",
 			obj->path);
 		err = -LIBBPF_ERRNO__FORMAT;