[pkg/dartdev] Enable Linux ARM cross-compilation on Windows.

The #ifdef block that would stop ARM cross-compilation on Windows
has been outdated for a few years now, as getting the target CPU features via TargetCPUFeatures is now handled appropriately on Windows.

TEST=ci, actual test depends on upload so will be in a followup CL

Issue: #28617
Change-Id: I9907145ec8fb97007769276cb3c6c2442ac9e17c
Cq-Include-Trybots: luci.dart.try:pkg-linux-release-arm64-try,pkg-linux-release-try,pkg-mac-release-arm64-try,pkg-mac-release-try,pkg-win-release-arm64-try,pkg-win-release-try,dart-sdk-linux-riscv64-try,dart-sdk-linux-arm64-try,dart-sdk-linux-try,dart-sdk-mac-try,dart-sdk-win-arm64-try,dart-sdk-win-try,dart-sdk-mac-arm64-try
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/440224
Commit-Queue: Tess Strickland <[email protected]>
Reviewed-by: Ivan Inozemtsev <[email protected]>

Author: sstrickl

pkg/dartdev/lib/src/commands/compile.dart

@@ -467,8 +467,7 @@ class CompileNativeCommand extends CompileSubcommandCommand {
   static const String exeCmdName = 'exe';
   static const String aotSnapshotCmdName = 'aot-snapshot';
   static final supportedTargetPlatforms = <Target>{
-    // ARM cross-compilation is not supported on Windows currently.
-    if (!Platform.isWindows) Target.linuxArm,
+    Target.linuxArm,
     Target.linuxArm64,
     Target.linuxRiscv64,
     Target.linuxX64

runtime/vm/compiler/assembler/assembler_arm.cc

@@ -14,13 +14,6 @@
 #include "vm/instructions.h"
 #include "vm/tags.h"
 
-// An extra check since we are assuming the existence of /proc/cpuinfo below.
-#if !defined(DART_INCLUDE_SIMULATOR) && !defined(__linux__) &&                 \
-    !defined(ANDROID) && !defined(DART_HOST_OS_IOS) &&                         \
-    !defined(DART_HOST_OS_MACOS)
-#error ARM cross-compile only supported on Linux, Android, iOS, and Mac
-#endif
-
 // For use by LR related macros (e.g. CLOBBERS_LR).
 #define __ this->
 

sdk/BUILD.gn

@@ -879,15 +879,11 @@ group("create_full_sdk") {
     # Do not include gen_snapshot binaries for cross-compilation into
     # SDK, but add them as a dependency, so that they are built.
     public_deps += [
+      "../runtime/bin:gen_snapshot_product_linux_arm",
       "../runtime/bin:gen_snapshot_product_linux_arm64",
       "../runtime/bin:gen_snapshot_product_linux_riscv64",
       "../runtime/bin:gen_snapshot_product_linux_x64",
     ]
-
-    # assembler_arm.cc disallows ARM cross-compilation on Windows.
-    if (!is_win) {
-      public_deps += [ "../runtime/bin:gen_snapshot_product_linux_arm" ]
-    }
   }
 }