Don't define |r_debug| and |link_map| on Android releases 21 and later

src/common/android/include/link.h

 // Copyright (c) 2012, Google Inc.
 // All rights reserved.
 //
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 // notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
@@ skipping 25 matching lines @@
 
 // TODO(rmcilroy): Remove this file once the ndk is updated for other
 // architectures - crbug.com/358831
 #if !defined(__aarch64__) && !defined(__x86_64__) && \
     !(defined(__mips__) && _MIPS_SIM == _ABI64)
 
 #ifdef __cplusplus
 extern "C" {
 #endif  // __cplusplus
 
+// The structures below are present in ndk 21 and later.
+#if defined(ANDROID) && ANDROID_VERSION <= 20

[rmcilroy, 2016/07/18 15:04:08]

I don't think the defined(ANDROID) is needed - these headers are only included
if building for Android. 

Also, where does ANDROID_VERSION come from? I don't think it is defined in the
NDK and we don't define it either in Breakpad or Chromium's build as far as I
can tell.

Instead you might have to do something like what's done in elf.h where we do,
for example:
#define Elf32_auxv_t  __bionic_Elf32_auxv_t
#define Elf64_auxv_t  __bionic_Elf64_auxv_t

Then undef this definition and redefine the structs here.

 struct r_debug {
   int              r_version;
   struct link_map* r_map;
   ElfW(Addr)       r_brk;
   enum {
     RT_CONSISTENT,
     RT_ADD,
     RT_DELETE }    r_state;
   ElfW(Addr)       r_ldbase;
 };
 
 struct link_map {
   ElfW(Addr)       l_addr;
   char*            l_name;
   ElfW(Dyn)*       l_ld;
   struct link_map* l_next;
   struct link_map* l_prev;
 };
+#endif
 
 #ifdef __cplusplus
 }  // extern "C"
 #endif  // __cplusplus
 
 #endif  // !defined(__aarch64__) && !defined(__x86_64__)
 
 #endif /* GOOGLE_BREAKPAD_ANDROID_INCLUDE_LINK_H */