Make upload_revision with Rust quick again

The --verify-stage0-hash flag was being executed in build_rust.py after
doing a bunch of git checkout and LLVM building, it should be a fast
return.

Since the upload_revision script already checked out the Rust git repo
it can also --skip-checkout.

Bug: 1401042
Change-Id: Idc9333fb0abbc3a5e0b549f1fc04cbc8fef9dc3b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4366658
Reviewed-by: Zequan Wu <[email protected]>
Commit-Queue: danakj <[email protected]>
Cr-Commit-Position: refs/heads/main@{#1121193}
NOKEYCHECK=True
GitOrigin-RevId: 3798deeaeea0f95642b3d8adcbc39f4746d6b3f2

Author: danakj

build_rust.py

@@ -633,18 +633,18 @@ def main():
     if not args.skip_checkout:
         CheckoutGitRepo('Rust', RUST_GIT_URL, checkout_revision, RUST_SRC_DIR)
 
-    (x86_64_llvm_config, aarch64_llvm_config,
-     target_llvm_dir) = BuildLLVMLibraries(args.skip_llvm_build,
-                                           args.build_mac_arm,
-                                           args.gcc_toolchain)
-
     VerifyStage0JsonHash()
     if args.verify_stage0_hash:
         # The above function exits and prints the actual hash if verification
         # failed so we just quit here; if we reach this point, the hash is
         # valid.
         return 0
 
+    (x86_64_llvm_config, aarch64_llvm_config,
+     target_llvm_dir) = BuildLLVMLibraries(args.skip_llvm_build,
+                                           args.build_mac_arm,
+                                           args.gcc_toolchain)
+
     AddCMakeToPath()
 
     # Require zlib compression.