Do not build temporal_capi with GN (which needs the Chromium Rust
toolchain).  Use the headers of the cargo-vendored crate, and link the
static library built from it in pre-build into executables that GN links
itself, such as mksnapshot.  The final deno binary gets the same code
through the v8 crate's cargo dependency on temporal_capi.

--- cargo-crates/v8-150.4.0/third_party/rust/temporal_capi/BUILD.gn.orig	2006-07-24 01:21:28 UTC
+++ cargo-crates/v8-150.4.0/third_party/rust/temporal_capi/BUILD.gn
@@ -29,10 +29,15 @@ group("temporal_capi") {
 group("temporal_capi") {
   public_configs = [
     ":temporal_capi_include_dirs",
+    ":temporal_capi_lib",
     ":temporal_capi_versioning_defines",
   ]
-  public_deps = [ "//third_party/rust/temporal_capi/v0_2:lib" ]
 }
 config("temporal_capi_include_dirs") {
-  include_dirs = [ "//third_party/rust/chromium_crates_io/vendor/temporal_capi-v0_2/bindings/cpp" ]
+  include_dirs = [ "%%TEMPORAL_CAPI_DIR%%/bindings/cpp" ]
+}
+
+# Prebuilt by cargo; needed by executables GN links itself, such as mksnapshot.
+config("temporal_capi_lib") {
+  libs = [ "%%TEMPORAL_CAPI_LIB%%" ]
 }