Fix building on musl libc.

src/common/linux/elf_core_dump.h

 // Copyright (c) 2011, 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 18 matching lines @@
 
 // elf_core_dump.h: Define the google_breakpad::ElfCoreDump class, which
 // encapsulates an ELF core dump file mapped into memory.
 
 #ifndef COMMON_LINUX_ELF_CORE_DUMP_H_
 #define COMMON_LINUX_ELF_CORE_DUMP_H_
 
 #include <elf.h>
 #include <link.h>
 #include <stddef.h>
+#include <sys/reg.h>
 
 #include "common/memory_range.h"
 
 namespace google_breakpad {
 
 // A class encapsulating an ELF core dump file mapped into memory, which
 // provides methods for accessing program headers and the note section.
 class ElfCoreDump {
  public:
   // ELF types based on the value of __WORDSIZE.
@@ skipping 90 matching lines @@
   Note GetFirstNote() const;
 
  private:
   // Core dump content.
   MemoryRange content_;
 };
 
 }  // namespace google_breakpad
 
 #endif  // COMMON_LINUX_ELF_CORE_DUMP_H_