[gn build] Add build file for llvm-objcopy

[thakis]

Summary

Needed by check-lld.

This should've been part of r349486 but I messed up.

[phosek]

LGTM

llvm/utils/gn/secondary/BUILD.gn

 group("default") {
   deps = [
     ":lld",
     "//llvm/tools/llc",
     "//llvm/tools/llvm-ar:symlinks",
     "//llvm/tools/llvm-as",
     "//llvm/tools/llvm-bcanalyzer",
     "//llvm/tools/llvm-dis",
     "//llvm/tools/llvm-dwarfdump",
     "//llvm/tools/llvm-mc",
     "//llvm/tools/llvm-nm:symlinks",
+    "//llvm/tools/llvm-objcopy:symlinks",
     "//llvm/tools/llvm-objdump:symlinks",
     "//llvm/tools/llvm-pdbutil",
     "//llvm/tools/llvm-readobj:symlinks",
     "//llvm/tools/llvm-undname",
     "//llvm/tools/obj2yaml",
     "//llvm/tools/opt",
     "//llvm/tools/yaml2obj",
     "//llvm/utils/FileCheck",
deps = [
     "//llvm/tools/llvm-ar:symlinks",
   ]
 }
 group("llvm-nm") {
   deps = [
     "//llvm/tools/llvm-nm:symlinks",
   ]
 }
+group("llvm-objcopy") {
+  deps = [
+    "//llvm/tools/llvm-objcopy:symlinks",
+  ]
+}
 group("llvm-objdump") {
   deps = [
     "//llvm/tools/llvm-objdump:symlinks",
   ]
 }
 group("llvm-readobj") {
   deps = [
     "//llvm/tools/llvm-readobj:symlinks",
   ]
 }
 
 # A pool called "console" in the root BUILD.gn is magic and represents ninja's
 # built-in console pool. (Requires a GN with `gn --version` >= 552353.)
 pool("console") {
   depth = 1
 }

llvm/utils/gn/secondary/llvm/tools/llvm-objcopy/BUILD.gn

+import("//llvm/tools/binutils_symlinks.gni")
+import("//llvm/utils/TableGen/tablegen.gni")
+import("//llvm/utils/gn/build/symlink_or_copy.gni")
+
+tablegen("ObjcopyOpts") {
+  visibility = [ ":llvm-objcopy" ]
+  args = [ "-gen-opt-parser-defs" ]
+}
+
+tablegen("StripOpts") {
+  visibility = [ ":llvm-objcopy" ]
+  args = [ "-gen-opt-parser-defs" ]
+}
+
+symlinks = [ "llvm-strip" ]
+if (llvm_install_binutils_symlinks) {
+  symlinks += [
+    "objcopy",
+    "strip",
+  ]
+}
+foreach(target, symlinks) {
+  symlink_or_copy(target) {
+    deps = [
+      ":llvm-objcopy",
+    ]
+    source = "llvm-objcopy"
+    output = "$root_out_dir/bin/$target"
+  }
+}
+
+# //:llvm-objcopy depends on this symlink target, see comment in //BUILD.gn.
+group("symlinks") {
+  deps = []
+  foreach(target, symlinks) {
+    deps += [ ":$target" ]
+  }
+}
+
+executable("llvm-objcopy") {
+  deps = [
+    ":ObjcopyOpts",
+    ":StripOpts",
+    "//llvm/lib/MC",
+    "//llvm/lib/Object",
+    "//llvm/lib/Option",
+    "//llvm/lib/Support",
+  ]
+  include_dirs = [ "." ]
+  sources = [
+    "Buffer.cpp",
+    "CopyConfig.cpp",
+    "ELF/ELFObjcopy.cpp",
+    "ELF/Object.cpp",
+    "llvm-objcopy.cpp",
+  ]
+}