don't build flutter SDK artifacts for armv7 (flutter/engine#28016)

engine/src/flutter/BUILD.gn

@@ -46,8 +46,11 @@ if (flutter_prebuilt_dart_sdk) {
 
 # Flutter SDK artifacts should only be built when either doing host builds, or
 # for cross-compiled desktop targets.
+# TODO: We can't build the engine artifacts for arm (32-bit) right now;
+# see https://github.com/flutter/flutter/issues/74322
 _build_engine_artifacts =
-    current_toolchain == host_toolchain || (is_linux && !is_chromeos) || is_mac
+    current_toolchain == host_toolchain ||
+    (is_linux && !is_chromeos && current_cpu != "arm") || is_mac
 
 group("dart_sdk") {
   if (_build_engine_artifacts) {

engine/src/flutter/tools/gn

@@ -88,7 +88,7 @@ def is_host_build(args):
     # target_os='linux' and linux-cpu='arm64'
     # TODO(fujino): make host platform explicit
     #   https://github.com/flutter/flutter/issues/79403
-    return args.target_os is None or args.target_os == 'linux'
+    return args.target_os is None or (args.target_os == 'linux' and args.linux_cpu == 'arm64')
 
 # Determines whether a prebuilt Dart SDK can be used instead of building one.
 # We can use a prebuilt Dart SDK when: