Use prctl(PR_CAPBSET_READ) to get the last valid cap on Android.

Not all Android processes will have access to '/proc/sys/kernel/cap_last_cap',
so use prctl() to get the last valid cap on Android.

Bug: 26217031
Change-Id: I7dffc8facca30a2e32c5c310c383e82a07b0519e
diff --git a/util.h b/util.h
index a88cbc8..069090f 100644
--- a/util.h
+++ b/util.h
@@ -29,6 +29,14 @@
 extern const char *log_syscalls[];
 extern const size_t log_syscalls_len;
 
+inline int is_android() {
+#if defined(__ANDROID__)
+	return 1;
+#else
+	return 0;
+#endif
+}
+
 int lookup_syscall(const char *name);
 const char *lookup_syscall_name(int nr);
 long int parse_constant(char *constant_str, char **endptr);