Add a header for linker LTO plugin

plugin.h

@@ -0,0 +1,115 @@
+#include <stdint.h>
+
+enum PluginStatus {
+  LDPS_OK,
+  LDPS_NO_SYMS,
+  LDPS_BAD_HANDLE,
+  LDPS_ERR,
+};
+
+enum PluginTag {
+  LDPT_NULL,
+  LDPT_API_VERSION,
+  LDPT_GOLD_VERSION,
+  LDPT_LINKER_OUTPUT,
+  LDPT_OPTION,
+  LDPT_REGISTER_CLAIM_FILE_HOOK,
+  LDPT_REGISTER_ALL_SYMBOLS_READ_HOOK,
+  LDPT_REGISTER_CLEANUP_HOOK,
+  LDPT_ADD_SYMBOLS,
+  LDPT_GET_SYMBOLS,
+  LDPT_ADD_INPUT_FILE,
+  LDPT_MESSAGE,
+  LDPT_GET_INPUT_FILE,
+  LDPT_RELEASE_INPUT_FILE,
+  LDPT_ADD_INPUT_LIBRARY,
+  LDPT_OUTPUT_NAME,
+  LDPT_SET_EXTRA_LIBRARY_PATH,
+  LDPT_GNU_LD_VERSION,
+  LDPT_GET_VIEW,
+  LDPT_GET_INPUT_SECTION_COUNT,
+  LDPT_GET_INPUT_SECTION_TYPE,
+  LDPT_GET_INPUT_SECTION_NAME,
+  LDPT_GET_INPUT_SECTION_CONTENTS,
+  LDPT_UPDATE_SECTION_ORDER,
+  LDPT_ALLOW_SECTION_ORDERING,
+  LDPT_GET_SYMBOLS_V2,
+  LDPT_ALLOW_UNIQUE_SEGMENT_FOR_SECTIONS,
+  LDPT_UNIQUE_SEGMENT_FOR_SECTIONS,
+  LDPT_GET_SYMBOLS_V3,
+  LDPT_GET_INPUT_SECTION_ALIGNMENT,
+  LDPT_GET_INPUT_SECTION_SIZE,
+  LDPT_REGISTER_NEW_INPUT_HOOK,
+  LDPT_GET_WRAP_SYMBOLS,
+  LDPT_ADD_SYMBOLS_V2,
+};
+
+struct PluginTagValue {
+  PluginTag tag;
+  union {
+    int val;
+    void *ptr;
+  };
+};
+
+enum PluginOutputFileType {
+  LDPO_REL,
+  LDPO_EXEC,
+  LDPO_DYN,
+  LDPO_PIE,
+};
+
+struct PluginInputFile {
+  const char *name;
+  int fd;
+  off_t offset;
+  off_t filesize;
+  void *handle;
+};
+
+struct PluginSymbol {
+  char *name;
+  char *version;
+  char def;
+  char symbol_type;
+  char section_kind;
+  int visibility;
+  uint64_t size;
+  char *comdat_key;
+  int resolution;
+};
+
+enum PluginSymbolKind {
+  LDPK_DEF,
+  LDPK_WEAKDEF,
+  LDPK_UNDEF,
+  LDPK_WEAKUNDEF,
+  LDPK_COMMON,
+};
+
+enum PluginSymbolVisibility {
+  LDPV_DEFAULT,
+  LDPV_PROTECTED,
+  LDPV_INTERNAL,
+  LDPV_HIDDEN,
+};
+
+enum PluginSymbolResolution {
+  LDPR_UNKNOWN,
+  LDPR_UNDEF,
+  LDPR_PREVAILING_DEF,
+  LDPR_PREVAILING_DEF_IRONLY,
+  LDPR_PREEMPTED_REG,
+  LDPR_PREEMPTED_IR,
+  LDPR_RESOLVED_IR,
+  LDPR_RESOLVED_EXEC,
+  LDPR_RESOLVED_DYN,
+  LDPR_PREVAILING_DEF_IRONLY_EXP,
+};
+
+enum PluginLevel {
+  LDPL_INFO,
+  LDPL_WARNING,
+  LDPL_ERROR,
+  LDPL_FATAL,
+};