Revert of Reland changes to v8_snapshot GN build arg. (patchset #2 id:20001 of...

Revert of Reland changes to v8_snapshot GN build arg. (patchset #2 id:20001 of https://codereview.chromium.org/1979883002/ )

Reason for revert:
Blocks the roll again:
https://codereview.chromium.org/1993163002/

https://build.chromium.org/p/tryserver.chromium.linux/builders/chromeos_amd64-generic_chromium_compile_only_ng/builds/140169

Lets add chromeos_amd64-generic_chromium_compile_only_ng on a reland as well.

Original issue's description:
> Reland changes to v8_snapshot GN build arg.
>
> This patch re-lands #36193 with a couple of minor tweaks
> including updating the BUILD.gn file to use the new
> variable name and incorporating thakis' request to support
> cross-compiling the win snapshot from a mac.
>
> R=thakis@chromium.org, jochen@chromium.org, machenbach@chromium.org
> BUG=608596, 595653
> CQ_INCLUDE_TRYBOTS=tryserver.chromium.linux:chromeos_daisy_chromium_compile_only_ng
>
> Committed: https://crrev.com/b6168e1223d266dba1a357a921bc84ae97a1d803
> Cr-Commit-Position: refs/heads/master@{#36342}

TBR=jochen@chromium.org,thakis@chromium.org,stevenjb@chromium.org,adamk@chromium.org,dpranke@chromium.org
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=608596, 595653

Review-Url: https://codereview.chromium.org/1996533002
Cr-Commit-Position: refs/heads/master@{#36347}

BUILD.gn

@@ -615,7 +615,7 @@ action("run_mksnapshot") {
   visibility = [ ":*" ]  # Only targets in this file can depend on this.
 
   deps = [
-    ":mksnapshot($v8_snapshot_toolchain)",
+    ":mksnapshot($snapshot_toolchain)",
   ]
 
   script = "tools/run.py"
@@ -625,7 +625,7 @@ action("run_mksnapshot") {
   ]
 
   args = [
-    "./" + rebase_path(get_label_info(":mksnapshot($v8_snapshot_toolchain)",
+    "./" + rebase_path(get_label_info(":mksnapshot($snapshot_toolchain)",
                                       "root_out_dir") + "/mksnapshot",
                        root_build_dir),
     "--startup_src",
@@ -2012,7 +2012,7 @@ v8_source_set("fuzzer_support") {
 # Executables
 #
 
-if (current_toolchain == v8_snapshot_toolchain) {
+if (current_toolchain == snapshot_toolchain) {
   executable("mksnapshot") {
     visibility = [ ":*" ]  # Only targets in this file can depend on this.
 
@@ -2114,7 +2114,7 @@ executable("d8") {
   }
 }
 
-if ((current_toolchain == host_toolchain && v8_toolset_for_shell == "host") || (current_toolchain == v8_snapshot_toolchain && v8_toolset_for_shell == "host") || (current_toolchain != host_toolchain && v8_toolset_for_shell == "target")) {
+if ((current_toolchain == host_toolchain && v8_toolset_for_shell == "host") || (current_toolchain == snapshot_toolchain && v8_toolset_for_shell == "host") || (current_toolchain != host_toolchain && v8_toolset_for_shell == "target")) {
   executable("v8_shell") {
     sources = [
       "samples/shell.cc",

snapshot_toolchain.gni

@@ -25,47 +25,22 @@
 # (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 # OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
-declare_args() {
-  # The snapshot needs to be compiled for the host, but compiled with
-  # a toolchain that matches the bit-width of the target.
-  v8_snapshot_toolchain = ""
-}
+# The snapshot needs to be compiled for the host, but compiled with
+# a toolchain that matches the bit-width of the target.
 
 # TODO(GYP): For now we only support 32-bit little-endian target builds from an
 # x64 Linux host. Eventually we need to support all of the host/target
 # configurations v8 runs on.
-if (v8_snapshot_toolchain == "") {
-  if (host_cpu == "x64" && host_os == "linux") {
-    if (target_cpu == "arm" || target_cpu == "mipsel" || target_cpu == "x86") {
-      if (target_os == "android" || is_clang) {
-        v8_snapshot_toolchain = "//build/toolchain/linux:clang_x86"
-      } else if (target_os == "chromeos") {
-        # TODO(dpranke): crbug.com/608596: Remove this clause once the
-        # CrOS ebuilds are setting v8_snapshot_toolchain directly and
-        # we've cleaned up the sysroot settings in //build.
-        v8_snapshot_toolchain = "//build/toolchain/linux:clang_x86"
-      } else {
-        v8_snapshot_toolchain = "//build/toolchain/linux:x86"
-      }
-
-    } else if (target_cpu == "x64" || target_cpu == "arm64" ||
-               target_cpu == "mips64el") {
-      if (target_os == "android" || is_clang) {
-        v8_snapshot_toolchain = "//build/toolchain/linux:clang_x64"
-      } else {
-        v8_snapshot_toolchain = "//build/toolchain/linux:x64"
-      }
-    } else {
-      assert(false, "Need environment for this arch: $target_cpu")
-    }
-  } else if (host_os == "mac" && target_os == "win") {
-    v8_snapshot_toolchain = "//build/toolchain/mac:clang_$target_cpu"
+if (host_cpu == "x64" && host_os == "linux") {
+  if (target_cpu == "arm" || target_cpu == "mipsel" || target_cpu == "x86") {
+    snapshot_toolchain = "//build/toolchain/linux:clang_x86"
+  } else if (target_cpu == "x64" || target_cpu == "arm64" || target_cpu == "mips64el") {
+    snapshot_toolchain = "//build/toolchain/linux:clang_x64"
   } else {
-    v8_snapshot_toolchain = default_toolchain
+    assert(false, "Need environment for this arch: $target_cpu")
   }
+} else {
+  snapshot_toolchain = default_toolchain
 }
 
-# TODO(dpranke): snapshot_toolchain is provided for backwards compatibility
-# and should be removed once all callers are updated to refer to
-# v8_snapshot_toolchain directly.
-snapshot_toolchain = v8_snapshot_toolchain
+