[gn build] Add build files for obj2yaml, yaml2obj, and lib/ObjectYAML

The two executables are needed by check-lld.

Differential Revision: https://reviews.llvm.org/D55687
diff --git a/llvm/utils/gn/secondary/BUILD.gn b/llvm/utils/gn/secondary/BUILD.gn
index c43a54c..24514a2 100644
--- a/llvm/utils/gn/secondary/BUILD.gn
+++ b/llvm/utils/gn/secondary/BUILD.gn
@@ -7,6 +7,8 @@
     "//llvm/tools/llvm-dwarfdump",
     "//llvm/tools/llvm-mc",
     "//llvm/tools/llvm-undname",
+    "//llvm/tools/obj2yaml",
+    "//llvm/tools/yaml2obj",
     "//llvm/utils/FileCheck",
     "//llvm/utils/count",
     "//llvm/utils/not",
diff --git a/llvm/utils/gn/secondary/llvm/lib/ObjectYAML/BUILD.gn b/llvm/utils/gn/secondary/llvm/lib/ObjectYAML/BUILD.gn
new file mode 100644
index 0000000..27367ff1
--- /dev/null
+++ b/llvm/utils/gn/secondary/llvm/lib/ObjectYAML/BUILD.gn
@@ -0,0 +1,22 @@
+static_library("ObjectYAML") {
+  output_name = "LLVMObjectYAML"
+  deps = [
+    "//llvm/lib/DebugInfo/CodeView",
+    "//llvm/lib/Support",
+  ]
+  sources = [
+    "COFFYAML.cpp",
+    "CodeViewYAMLDebugSections.cpp",
+    "CodeViewYAMLSymbols.cpp",
+    "CodeViewYAMLTypeHashing.cpp",
+    "CodeViewYAMLTypes.cpp",
+    "DWARFEmitter.cpp",
+    "DWARFVisitor.cpp",
+    "DWARFYAML.cpp",
+    "ELFYAML.cpp",
+    "MachOYAML.cpp",
+    "ObjectYAML.cpp",
+    "WasmYAML.cpp",
+    "YAML.cpp",
+  ]
+}
diff --git a/llvm/utils/gn/secondary/llvm/tools/obj2yaml/BUILD.gn b/llvm/utils/gn/secondary/llvm/tools/obj2yaml/BUILD.gn
new file mode 100644
index 0000000..6ba2022
--- /dev/null
+++ b/llvm/utils/gn/secondary/llvm/tools/obj2yaml/BUILD.gn
@@ -0,0 +1,18 @@
+executable("obj2yaml") {
+  deps = [
+    "//llvm/lib/DebugInfo/CodeView",
+    "//llvm/lib/DebugInfo/DWARF",
+    "//llvm/lib/Object",
+    "//llvm/lib/ObjectYAML",
+    "//llvm/lib/Support",
+  ]
+  sources = [
+    "Error.cpp",
+    "coff2yaml.cpp",
+    "dwarf2yaml.cpp",
+    "elf2yaml.cpp",
+    "macho2yaml.cpp",
+    "obj2yaml.cpp",
+    "wasm2yaml.cpp",
+  ]
+}
diff --git a/llvm/utils/gn/secondary/llvm/tools/yaml2obj/BUILD.gn b/llvm/utils/gn/secondary/llvm/tools/yaml2obj/BUILD.gn
new file mode 100644
index 0000000..56bebc4
--- /dev/null
+++ b/llvm/utils/gn/secondary/llvm/tools/yaml2obj/BUILD.gn
@@ -0,0 +1,16 @@
+executable("yaml2obj") {
+  deps = [
+    "//llvm/lib/DebugInfo/CodeView",
+    "//llvm/lib/MC",
+    "//llvm/lib/Object",
+    "//llvm/lib/ObjectYAML",
+    "//llvm/lib/Support",
+  ]
+  sources = [
+    "yaml2coff.cpp",
+    "yaml2elf.cpp",
+    "yaml2macho.cpp",
+    "yaml2obj.cpp",
+    "yaml2wasm.cpp",
+  ]
+}