Revert of Change v8_snapshot_toolchain to be a GN build arg.

snapshot_toolchain.gni

Index: snapshot_toolchain.gni
diff --git a/snapshot_toolchain.gni b/snapshot_toolchain.gni
index 7e96720ce88bbf68b82515ea981d3615e23ddd77..4932110489dd1a7fe65a6124aa655192661d3bd6 100644
--- a/snapshot_toolchain.gni
+++ b/snapshot_toolchain.gni
@@ -25,40 +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 {
-        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")
-    }
+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(GYP): 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
+