[infra] Assembles the SDK using GN rather than create_sdk.py

BUILD.gn

Index: BUILD.gn
diff --git a/BUILD.gn b/BUILD.gn
index f37232f4b799773700f71f6d7c5a259b572a0f6d..e12a15e5fc6edf25b8fc1614593c33ae4a04256c 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -4,7 +4,7 @@
 
 # This target will be built if no target is specified when invoking ninja.
 group("default") {
-  if (defined(is_fuchsia) && (is_fuchsia || is_fuchsia_host)) {
+  if (is_fuchsia || is_fuchsia_host) {
     # Fuchsia has run_vm_tests marked testonly.
     testonly = true
   }
@@ -14,7 +14,7 @@ group("default") {
 }
 
 group("most") {
-  if (defined(is_fuchsia) && (is_fuchsia || is_fuchsia_host)) {
+  if (is_fuchsia || is_fuchsia_host) {
     # Fuchsia has run_vm_tests marked testonly.
     testonly = true
   }
@@ -30,7 +30,7 @@ group("most") {
 }
 
 group("runtime") {
-  if (defined(is_fuchsia) && (is_fuchsia || is_fuchsia_host)) {
+  if (is_fuchsia || is_fuchsia_host) {
     # Fuchsia has run_vm_tests marked testonly.
     testonly = true
   }
@@ -46,7 +46,7 @@ group("runtime") {
 }
 
 group("runtime_kernel") {
-  if (defined(is_fuchsia) && (is_fuchsia || is_fuchsia_host)) {
+  if (is_fuchsia || is_fuchsia_host) {
     # Fuchsia has run_vm_tests marked testonly.
     testonly = true
   }
@@ -121,85 +121,83 @@ group("samples") {
 # The rules below build a qemu Fuchsia OS image that includes the Dart tree
 # under /system/test/dart. Building this image is gated by the GN argument
 # 'dart_build_fuchsia_test_image' because building the image is slow.
-if (defined(is_fuchsia) && is_fuchsia) {
+if (is_fuchsia) {
   declare_args() {
     dart_build_fuchsia_test_image = false
   }
 
-  if (dart_build_fuchsia_test_image) {
-    action("generate_dart_test_manifest") {
-      testonly = true
-
-      deps = [
-        "//packages/gn:mkbootfs",
-      ]
-
-      output_prefix = "$target_gen_dir/dart_test_tree"
-      outputs = [
-        "$output_prefix.manifest",
-      ]
-
-      mode = "release"
-      if (is_debug) {
-        mode = "debug"
-      }
-
-      mkbootfs_gen = get_label_info("//packages/gn:mkbootfs", "target_gen_dir")
-      user_manifest = "$mkbootfs_gen/user.bootfs.manifest"
-
-      script = "tools/gen_fuchsia_test_manifest.py"
-      args = [
-        "-m",
-        mode,
-        "-u",
-        rebase_path(user_manifest),
-        "-o",
-        rebase_path(output_prefix),
-      ]
+  action("generate_dart_test_manifest") {
+    testonly = true
+
+    deps = [
+      "//packages/gn:mkbootfs",
+    ]
+
+    output_prefix = "$target_gen_dir/dart_test_tree"
+    outputs = [
+      "$output_prefix.manifest",
+    ]
+
+    mode = "release"
+    if (is_debug) {
+      mode = "debug"
     }
 
-    action("generate_dart_test_image") {
-      testonly = true
-      deps = [
-        ":generate_dart_test_manifest",
-        "runtime/bin:dart",
-        "runtime/bin:process_test",
-        "runtime/bin:run_vm_tests",
-      ]
-
-      # Compute path to magenta bootdata.bin
-      if (current_cpu == "arm64") {
-        magenta_bootdata =
-            "//out/build-magenta/build-magenta-qemu-arm64/bootdata.bin"
-      } else if (current_cpu == "x64") {
-        magenta_bootdata =
-            "//out/build-magenta/build-magenta-pc-x86-64/bootdata.bin"
-      } else {
-        assert(false, "unable to determine path to magenta's bootdata.bin")
-      }
-
-      input = "$target_gen_dir/dart_test_tree.manifest"
-      inputs = [
-        magenta_bootdata,
-        input,
-      ]
-
-      output = "$root_out_dir/dart_test_tree.bin"
-      outputs = [
-        output,
-      ]
-
-      script = "//packages/gn/make_bootfs.py"
-      args = [
-        "--manifest",
-        rebase_path(input),
-        "--output-file",
-        rebase_path(output),
-        "--build-id-map",
-        rebase_path("$target_gen_dir/build_id_map"),
-        "--pre-binaries",
-        rebase_path(magenta_bootdata),
-      ]
+    mkbootfs_gen = get_label_info("//packages/gn:mkbootfs", "target_gen_dir")
+    user_manifest = "$mkbootfs_gen/user.bootfs.manifest"
+
+    script = "tools/gen_fuchsia_test_manifest.py"
+    args = [
+      "-m",
+      mode,
+      "-u",
+      rebase_path(user_manifest),
+      "-o",
+      rebase_path(output_prefix),
+    ]
+  }
+
+  action("generate_dart_test_image") {
+    testonly = true
+    deps = [
+      ":generate_dart_test_manifest",
+      "runtime/bin:dart",
+      "runtime/bin:process_test",
+      "runtime/bin:run_vm_tests",
+    ]
+
+    # Compute path to magenta bootdata.bin
+    if (current_cpu == "arm64") {
+      magenta_bootdata =
+          "//out/build-magenta/build-magenta-qemu-arm64/bootdata.bin"
+    } else if (current_cpu == "x64") {
+      magenta_bootdata =
+          "//out/build-magenta/build-magenta-pc-x86-64/bootdata.bin"
+    } else {
+      assert(false, "unable to determine path to magenta's bootdata.bin")
     }
+
+    input = "$target_gen_dir/dart_test_tree.manifest"
+    inputs = [
+      magenta_bootdata,
+      input,
+    ]
+
+    output = "$root_out_dir/dart_test_tree.bin"
+    outputs = [
+      output,
+    ]
+
+    script = "//packages/gn/make_bootfs.py"
+    args = [
+      "--manifest",
+      rebase_path(input),
+      "--output-file",
+      rebase_path(output),
+      "--build-id-map",
+      rebase_path("$target_gen_dir/build_id_map"),
+      "--pre-binaries",
+      rebase_path(magenta_bootdata),
+    ]
   }
 }