[gn build] Add lldb to default target on Windows

[thakis]

Summary

It seems to build fine (even though some tests fail), so might
as well let the bots build it. If it turns out to break a lot,
we can always turn it back off.

[hans]

Sgtm.

llvm/utils/gn/secondary/BUILD.gn

 import("//clang/lib/ARCMigrate/enable.gni")
 import("//clang/lib/StaticAnalyzer/Frontend/enable.gni")
 import("//llvm/utils/gn/build/toolchain/compiler.gni")
 
 group("default") {
   deps = [
     "//clang-tools-extra/clangd/test",
     "//clang-tools-extra/test",
     "//clang/test",
     "//clang/tools/scan-build",
     "//compiler-rt",
     "//compiler-rt/include",
     "//compiler-rt/lib/scudo",
     "//lld/test",
+    "//lldb/test",
     "//llvm/test",
   ]
   if (current_os == "linux") {
     deps += [
       "//libcxx",
       "//libcxxabi",
     ]
   }
-  if (current_os == "linux" || current_os == "mac") {
-    deps += [ "//lldb/test" ]
-  }
   if (current_os == "linux" || current_os == "android") {
     deps += [ "//compiler-rt/test/hwasan" ]
   }
   if (current_os == "linux" || current_os == "mac") {
     deps += [ "//libunwind" ]
   }
 
   testonly = true