Reapply "[fuchsia] Prepare for setting the Dart target architecture appropriately in the host binar…

runtime/BUILD.gn

Index: runtime/BUILD.gn
diff --git a/runtime/BUILD.gn b/runtime/BUILD.gn
index 2713c7c6ec8528adb7050ede86c754fd2d24ea5d..caf6496fac155570cdad0e10e9541b9245e165e1 100644
--- a/runtime/BUILD.gn
+++ b/runtime/BUILD.gn
@@ -72,27 +72,11 @@ config("dart_no_snapshot_config") {
   defines += [ "DART_NO_SNAPSHOT" ]
 }
 
-config("dart_config") {
+# TODO(rmacnak): If Fuchsia adds a checked-in SDK, this should be folded back
+# into dart_config
+config("dart_use_target_arch_config") {
   defines = []
 
-  if (target_os == "android") {
-    defines += [ "TARGET_OS_ANDROID" ]
-  } else if (target_os == "fuchsia") {
-    defines += [ "TARGET_OS_FUCHSIA" ]
-  } else if (target_os == "ios") {
-    defines += [ "TARGET_OS_MACOS" ]
-    defines += [ "TARGET_OS_MACOS_IOS" ]
-  } else if (target_os == "linux") {
-    defines += [ "TARGET_OS_LINUX" ]
-  } else if (target_os == "mac") {
-    defines += [ "TARGET_OS_MACOS" ]
-  } else if (target_os == "win") {
-    defines += [ "TARGET_OS_WINDOWS" ]
-  } else {
-    print("Unknown target_os: $target_os")
-    assert(false)
-  }
-
   if (dart_target_arch != "") {
     if (dart_target_arch == "arm" || dart_target_arch == "simarm") {
       defines += [ "TARGET_ARCH_ARM" ]
@@ -122,6 +106,28 @@ config("dart_config") {
       assert(false)
     }
   }
+}
+
+config("dart_config") {
+  defines = []
+
+  if (target_os == "android") {
+    defines += [ "TARGET_OS_ANDROID" ]
+  } else if (target_os == "fuchsia") {
+    defines += [ "TARGET_OS_FUCHSIA" ]
+  } else if (target_os == "ios") {
+    defines += [ "TARGET_OS_MACOS" ]
+    defines += [ "TARGET_OS_MACOS_IOS" ]
+  } else if (target_os == "linux") {
+    defines += [ "TARGET_OS_LINUX" ]
+  } else if (target_os == "mac") {
+    defines += [ "TARGET_OS_MACOS" ]
+  } else if (target_os == "win") {
+    defines += [ "TARGET_OS_WINDOWS" ]
+  } else {
+    print("Unknown target_os: $target_os")
+    assert(false)
+  }
 
   if (dart_debug) {
     defines += [ "DEBUG" ]
@@ -223,6 +229,7 @@ template("libdart_library") {
 }
 
 libdart_library("libdart_jit") {
+  extra_configs = [ ":dart_use_target_arch_config" ]
   extra_deps = [
     "vm:libdart_lib_jit",
     "vm:libdart_vm_jit",
@@ -230,7 +237,10 @@ libdart_library("libdart_jit") {
 }
 
 libdart_library("libdart_precompiled_runtime") {
-  extra_configs = [ ":dart_precompiled_runtime_config" ]
+  extra_configs = [
+    ":dart_precompiled_runtime_config",
+    ":dart_use_target_arch_config",
+  ]
   extra_deps = [
     "vm:libdart_lib_precompiled_runtime",
     "vm:libdart_vm_precompiled_runtime",
@@ -241,6 +251,7 @@ libdart_library("libdart_nosnapshot_with_precompiler") {
   extra_configs = [
     ":dart_no_snapshot_config",
     ":dart_precompiler_config",
+    ":dart_use_target_arch_config",
   ]
   extra_deps = [
     "vm:libdart_lib_nosnapshot_with_precompiler",
@@ -248,8 +259,23 @@ libdart_library("libdart_nosnapshot_with_precompiler") {
   ]
 }
 
+# TODO(rmacnak): Remove if Fuchsia adds a checked-in SDK.
+libdart_library("libdart_nosnapshot_with_precompiler_host_arch") {
+  extra_configs = [
+    ":dart_no_snapshot_config",
+    ":dart_precompiler_config",
+  ]
+  extra_deps = [
+    "vm:libdart_lib_nosnapshot_with_precompiler_host_arch",
+    "vm:libdart_vm_nosnapshot_with_precompiler_host_arch",
+  ]
+}
+
 libdart_library("libdart_with_precompiler") {
-  extra_configs = [ ":dart_precompiler_config" ]
+  extra_configs = [
+    ":dart_precompiler_config",
+    ":dart_use_target_arch_config",
+  ]
   extra_deps = [
     "vm:libdart_lib_with_precompiler",
     "vm:libdart_vm_with_precompiler",