Add skip_pip_install to build.py (microsoft#25982)

### Description
<!-- Describe your changes. -->
- Introduce a new command-line flag `--skip_pip_install`, similar to the
existing `--skip_submodule_sync`, to allow users to prevent `build.py`
from modifying their current Python environment.

### Motivation and Context
<!-- - Why is this change required? What problem does it solve?
- If it fixes an open issue, please link to the issue here. -->
- This is useful for scenarios where dependencies are already managed
externally or when users want to avoid unintended changes during the
build process.

Author: qti-hungjuiw

tools/ci_build/build.py

@@ -1738,7 +1738,12 @@ def run_onnxruntime_tests(args, source_dir, ctest_path, build_dir, configs):
             if is_windows():
                 cwd = os.path.join(cwd, config)
 
-            if args.enable_transformers_tool_test and not args.disable_contrib_ops and not args.use_rocm:
+            if (
+                not args.skip_pip_install
+                and args.enable_transformers_tool_test
+                and not args.disable_contrib_ops
+                and not args.use_rocm
+            ):
                 # PyTorch is required for transformers tests, and optional for some python tests.
                 # Install cpu only version of torch when cuda is not enabled in Linux.
                 extra = [] if args.use_cuda and is_linux() else ["--index-url", "https://download.pytorch.org/whl/cpu"]
@@ -1822,21 +1827,23 @@ def run_onnxruntime_tests(args, source_dir, ctest_path, build_dir, configs):
 
                         numpy_init_version = numpy.__version__
                         pb_init_version = google.protobuf.__version__
-                        run_subprocess(
-                            [
-                                sys.executable,
-                                "-m",
-                                "pip",
-                                "install",
-                                "-r",
-                                "requirements/transformers-test/requirements.txt",
-                            ],
-                            cwd=SCRIPT_DIR,
-                        )
+                        if not args.skip_pip_install:
+                            run_subprocess(
+                                [
+                                    sys.executable,
+                                    "-m",
+                                    "pip",
+                                    "install",
+                                    "-r",
+                                    "requirements/transformers-test/requirements.txt",
+                                ],
+                                cwd=SCRIPT_DIR,
+                            )
                         run_subprocess([sys.executable, "-m", "pytest", "--durations=0", "transformers"], cwd=cwd)
-                        # Restore initial numpy/protobuf version in case other tests use it
-                        run_subprocess([sys.executable, "-m", "pip", "install", "numpy==" + numpy_init_version])
-                        run_subprocess([sys.executable, "-m", "pip", "install", "protobuf==" + pb_init_version])
+                        if not args.skip_pip_install:
+                            # Restore initial numpy/protobuf version in case other tests use it
+                            run_subprocess([sys.executable, "-m", "pip", "install", "numpy==" + numpy_init_version])
+                            run_subprocess([sys.executable, "-m", "pip", "install", "protobuf==" + pb_init_version])
 
                 if not args.disable_ml_ops:
                     run_subprocess(
@@ -2524,7 +2531,7 @@ def main():
             log.info("Activating emsdk...")
             run_subprocess([emsdk_file, "activate", emsdk_version], cwd=emsdk_dir)
 
-        if args.enable_pybind and is_windows():
+        if not args.skip_pip_install and args.enable_pybind and is_windows():
             run_subprocess(
                 [sys.executable, "-m", "pip", "install", "-r", "requirements/pybind/requirements.txt"],
                 cwd=SCRIPT_DIR,

tools/ci_build/build_args.py

@@ -186,6 +186,7 @@ def add_cmake_build_config_args(parser: argparse.ArgumentParser) -> None:
         "--use_vcpkg_ms_internal_asset_cache", action="store_true", help="[MS Internal] Use internal vcpkg asset cache."
     )
     parser.add_argument("--skip_submodule_sync", action="store_true", help="Skip 'git submodule update'.")
+    parser.add_argument("--skip_pip_install", action="store_true", help="Skip 'pip install'.")
 
 
 def add_testing_args(parser: argparse.ArgumentParser) -> None: