[Fuchsia] Remove the legacy gn build rules for fuchsia

The updated test-scripts contains https://crrev.com/c/5341620 which
allows to generate fidl apis with an env var controlled location
rather than a hard-coded one. So the existing fuchsia gn build rules
in dart/sdk become obsolete and can be fully removed in favor of the
one in //third_party/fuchsia/gn-sdk/.

Meanwhile the gn-sdk has been updated with
https://crrev.com/c/5325282 to use api-level version'ed idk but not
the ones in arch/.

Cq-Include-Trybots: luci.dart.try:vm-fuchsia-release-arm64-try,vm-fuchsia-release-x64-try
Tested: ^^^^^
Bug: 40935282
Change-Id: I2ce958e6db1ff8221beef7b7ff953c32bb4525ba
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/355283
Reviewed-by: Ryan Macnak <[email protected]>
Reviewed-by: Alexander Thomas <[email protected]>
Commit-Queue: Zijie He <[email protected]>

Author: zijiehe-google-com

DEPS

@@ -700,7 +700,7 @@ Var("dart_root") + "/third_party/pkg/tar":
     "packages": [
       {
       "package": "chromium/fuchsia/test-scripts",
-      "version": "version:2@49064713a73ae92d8c28164938b97869afd336aa",
+      "version": "EAdD2YcYwVrhF2q_zR6xUvPkcKlPb1tJyM_6_oOc84kC",
       }
     ],
     "condition": 'download_fuchsia_deps',
@@ -711,7 +711,7 @@ Var("dart_root") + "/third_party/pkg/tar":
     "packages": [
       {
       "package": "chromium/fuchsia/gn-sdk",
-      "version": "version:2@7f1f23fce153ca079a77492d9d47d803d60b774e",
+      "version": "RgErspyYHapUO2SpcW-vo2p8yaRUMUrq0eWjRVPfQjoC",
       }
     ],
     "condition": 'download_fuchsia_deps',
@@ -836,6 +836,16 @@ hooks = [
         Var('emsdk_ver')],
     'condition': 'download_emscripten'
   },
+  {
+    'name': 'Erase arch/ from fuchsia sdk',
+    'pattern': '.',
+    'action': [
+      'rm',
+      '-rf',
+      'sdk/third_party/fuchsia/sdk/linux/arch',
+    ],
+    'condition': 'download_fuchsia_deps'
+  },
   {
     'name': 'Download Fuchsia system images',
     'pattern': '.',
@@ -847,4 +857,14 @@ hooks = [
     ],
     'condition': 'download_fuchsia_deps'
   },
+  {
+    'name': 'Generate Fuchsia GN build rules',
+    'pattern': '.',
+    'action': [
+      'python3',
+      'sdk/build/fuchsia/with_envs.py',
+      'sdk/third_party/fuchsia/test_scripts/gen_build_defs.py',
+    ],
+    'condition': 'download_fuchsia_deps'
+  },
 ]

build/config/BUILDCONFIG.gn

@@ -257,9 +257,7 @@ if (is_win) {
     "//build/config/win:winver",
   ]
   if (is_clang) {
-    _native_compiler_configs += [
-      "//build/config/win:relative_paths",
-    ]
+    _native_compiler_configs += [ "//build/config/win:relative_paths" ]
   }
 }
 if (is_posix) {
@@ -270,8 +268,8 @@ if (is_posix) {
 }
 if (is_fuchsia) {
   _native_compiler_configs += [
-    "//build/config/fuchsia:compiler",
-    "//build/config/fuchsia:runtime_library",
+    "//third_party/fuchsia/gn-sdk/src/config:compiler",
+    "//third_party/fuchsia/gn-sdk/src/config:runtime_library",
   ]
 }
 
@@ -450,8 +448,8 @@ foreach(_target_type,
         }
         if (is_fuchsia) {
           deps += [
-            "//build/config/fuchsia:runtime_library_group",
             "//build/fuchsia/config/clang:c++-runtime-deps",
+            "//third_party/fuchsia/gn-sdk/src/config:runtime_library_group",
           ]
         }
       }