[build] Make build_analyze_snapshot consistent between the host and…

… target toolchains.

Bug: #51242
Change-Id: I7a0ad1f0bc94c4593412945e4887f9045693fd40
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/280782
Reviewed-by: Daco Harkes <dacoharkes@google.com>
Commit-Queue: Ryan Macnak <rmacnak@google.com>

runtime/runtime_args.gni

@@ -92,6 +92,6 @@ declare_args() {
   # The analyze_snapshot tool is only supported on 64 bit AOT builds running
   # under linux and android platforms
   build_analyze_snapshot =
-      (is_linux || is_android) &&
+      (target_os == "linux" || target_os == "android") &&
       (dart_target_arch == "x64" || dart_target_arch == "arm64")
 }