Remove a few glibc #if hacks.

We've updated the corresponding glibc headers so we don't need these
hacks any more.

Bug: http://b/318541070
Test: treehugger
Change-Id: Ic1974f30f9edb2589cc93041822706bc89909882
diff --git a/tests/ifaddrs_test.cpp b/tests/ifaddrs_test.cpp
index 95562be..b3ab94d 100644
--- a/tests/ifaddrs_test.cpp
+++ b/tests/ifaddrs_test.cpp
@@ -20,13 +20,16 @@
 
 #include <dirent.h>
 #include <fcntl.h>
-#include <linux/if_packet.h>
 #include <net/ethernet.h>
 #include <net/if.h>
 #include <netdb.h>
 #include <netinet/in.h>
 #include <sys/ioctl.h>
 
+// (glibc as of 2.37 has redefinitions if you include these before <net/if.h>.)
+#include <linux/if.h>
+#include <linux/if_packet.h>
+
 #include <algorithm>
 #include <map>
 #include <thread>
@@ -211,15 +214,9 @@
   if ((flags & IFF_PORTSEL) != 0) result += " PORTSEL";
   if ((flags & IFF_AUTOMEDIA) != 0) result += " AUTOMEDIA";
   if ((flags & IFF_DYNAMIC) != 0) result += " DYNAMIC";
-#if defined(IFF_LOWER_UP)
   if ((flags & IFF_LOWER_UP) != 0) result += " LOWER_UP";
-#endif
-#if defined(IFF_DORMANT)
   if ((flags & IFF_DORMANT) != 0) result += " DORMANT";
-#endif
-#if defined(IFF_ECHO)
   if ((flags & IFF_ECHO) != 0) result += " ECHO";
-#endif
   return result;
 }