[gn build] Add build file for llvm-bcanalyzer

[thakis]

Summary

Needed for check-lld.

I missed this in previous patches.

llvm/trunk/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-objdump:symlinks",
     "//llvm/tools/llvm-readobj:symlinks",
     "//llvm/tools/llvm-undname",
     "//llvm/tools/obj2yaml",

llvm/trunk/utils/gn/secondary/llvm/tools/llvm-bcanalyzer/BUILD.gn

+executable("llvm-bcanalyzer") {
+  deps = [
+    "//llvm/lib/Bitcode/Reader",
+    "//llvm/lib/Support",
+  ]
+  sources = [
+    "llvm-bcanalyzer.cpp",
+  ]
+}