Reland "Add Linux ARM and Linux RISCV64 cross compilation gen_snapshot binaries."

This is a reland of commit d257c52309

Removes the dependency on gen_snapshot_linux_arm when building the
SDK for Windows.

TEST=ci (including pkg and sdk Windows trybots)

Original change's description:
> Add Linux ARM and Linux RISCV64 cross compilation gen_snapshot binaries.
>
> TEST=ci
>
> Issue: https://github.com/dart-lang/sdk/issues/28617
> Change-Id: Ia458f167c0e75fe9c7e31684bfaf9967499e9cda
> Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/437720
> Commit-Queue: Tess Strickland <sstrickl@google.com>
> Reviewed-by: Ivan Inozemtsev <iinozemtsev@google.com>

Change-Id: I19987ce794452340ee1cb7e49e14f6dac5532b42
Cq-Include-Trybots: luci.dart.try:pkg-win-release-arm64-try,pkg-win-release-try,dart-sdk-win-arm64-try,dart-sdk-win-try
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/438120
Reviewed-by: Martin Kustermann <kustermann@google.com>
Commit-Queue: Tess Strickland <sstrickl@google.com>
Reviewed-by: Ivan Inozemtsev <iinozemtsev@google.com>

runtime/BUILD.gn

@@ -149,6 +149,26 @@ config("dart_linux_x64_config") {
   ]
 }
 
+# We need to build gen_snapshot targeting Linux ARM during a build
+# of the SDK. This configuration is used to unconditionally target
+# Linux ARM. It should not be combined with dart_os_config and dart_arch_config.
+config("dart_linux_arm_config") {
+  defines = [
+    "DART_TARGET_OS_LINUX",
+    "TARGET_ARCH_ARM",
+  ]
+}
+
+# We need to build gen_snapshot targeting Linux RISCV64 during a build
+# of the SDK. This configuration is used to unconditionally target
+# Linux RISCV64. It should not be combined with dart_os_config and dart_arch_config.
+config("dart_linux_riscv64_config") {
+  defines = [
+    "DART_TARGET_OS_LINUX",
+    "TARGET_ARCH_RISCV64",
+  ]
+}
+
 config("dart_arch_config") {
   defines = []
 

runtime/bin/BUILD.gn

@@ -109,6 +109,20 @@ build_libdart_builtin("libdart_builtin_product_linux_arm64") {
   ]
 }
 
+build_libdart_builtin("libdart_builtin_product_linux_arm") {
+  extra_configs = [
+    "..:dart_product_config",
+    "..:dart_linux_arm_config",
+  ]
+}
+
+build_libdart_builtin("libdart_builtin_product_linux_riscv64") {
+  extra_configs = [
+    "..:dart_product_config",
+    "..:dart_linux_riscv64_config",
+  ]
+}
+
 template("build_native_assets_api") {
   extra_configs = []
   if (defined(invoker.extra_configs)) {
@@ -366,6 +380,33 @@ build_gen_snapshot("gen_snapshot_product_linux_arm64") {
     "../platform:libdart_platform_precompiler_product_linux_arm64",
   ]
 }
+
+build_gen_snapshot("gen_snapshot_product_linux_arm") {
+  extra_configs = [
+    "..:dart_product_config",
+    "..:dart_linux_arm_config",
+  ]
+  extra_deps = [
+    ":gen_snapshot_dart_io_product_linux_arm",
+    ":libdart_builtin_product_linux_arm",
+    "..:libdart_precompiler_product_linux_arm",
+    "../platform:libdart_platform_precompiler_product_linux_arm",
+  ]
+}
+
+build_gen_snapshot("gen_snapshot_product_linux_riscv64") {
+  extra_configs = [
+    "..:dart_product_config",
+    "..:dart_linux_riscv64_config",
+  ]
+  extra_deps = [
+    ":gen_snapshot_dart_io_product_linux_riscv64",
+    ":libdart_builtin_product_linux_riscv64",
+    "..:libdart_precompiler_product_linux_riscv64",
+    "../platform:libdart_platform_precompiler_product_linux_riscv64",
+  ]
+}
+
 build_gen_snapshot("gen_snapshot_host_targeting_host") {
   extra_configs = [ "..:dart_maybe_product_config" ]
   extra_deps = [
@@ -468,6 +509,20 @@ build_gen_snapshot_dart_io("gen_snapshot_dart_io_product_linux_arm64") {
   ]
 }
 
+build_gen_snapshot_dart_io("gen_snapshot_dart_io_product_linux_arm") {
+  extra_configs = [
+    "..:dart_product_config",
+    "..:dart_linux_arm_config",
+  ]
+}
+
+build_gen_snapshot_dart_io("gen_snapshot_dart_io_product_linux_riscv64") {
+  extra_configs = [
+    "..:dart_product_config",
+    "..:dart_linux_riscv64_config",
+  ]
+}
+
 # A source set for the implementation of 'dart:io' library.
 template("dart_io") {
   extra_configs = []

runtime/configs.gni

@@ -63,6 +63,18 @@ _precompiler_product_linux_arm64_config =
       "$_dart_runtime:dart_linux_arm64_config",
     ] + _product + _precompiler_base
 
+_precompiler_product_linux_arm_config =
+    [
+      "$_dart_runtime:dart_config",
+      "$_dart_runtime:dart_linux_arm_config",
+    ] + _product + _precompiler_base
+
+_precompiler_product_linux_riscv64_config =
+    [
+      "$_dart_runtime:dart_config",
+      "$_dart_runtime:dart_linux_riscv64_config",
+    ] + _product + _precompiler_base
+
 _all_configs = [
   {
     suffix = "_jit"
@@ -148,6 +160,20 @@ _all_configs = [
     compiler = true
     is_product = true
   },
+  {
+    suffix = "_precompiler_product_linux_arm"
+    configs = _precompiler_product_linux_arm_config
+    snapshot = false
+    compiler = true
+    is_product = true
+  },
+  {
+    suffix = "_precompiler_product_linux_riscv64"
+    configs = _precompiler_product_linux_riscv64_config
+    snapshot = false
+    compiler = true
+    is_product = true
+  },
 ]
 
 # This template creates a target for each of the configurations listed above.

sdk/BUILD.gn

@@ -880,8 +880,14 @@ group("create_full_sdk") {
     # SDK, but add them as a dependency, so that they are built.
     public_deps += [
       "../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" ]
+    }
   }
 }