Improve the Rust Windows toolchain build on workstations

Pass the `--build` on the install step, as on Windows some machines
may decide to target x86_64-pc-windows-gnu instead of
x86_64-pc-windows-msvc when it's not specified.

Add `.exe` suffix on the clang/llvm binary paths. Without it the
bootstrap tool can run them but can't "find" them and this causes
errors which then cause it to rebuild everything every time, even
rebuilding things multiple times across the build_rust.py steps. This
should also make the bot build faster.

Warn if the sh.exe is coming from gnubby as that is a cygwin shell
and it can't handle normalized unix-style paths like git bash can.
The Rust install will fail if trying to use that shell. Since it needs
to be first in the PATH for other things, let --sh specify the path to
Git's shell and then insert that at the front of PATH for the duration
of build_rust.py.

Avoid dirtying files by downloading zlib when using --skip-checkout
so that it's quicker to rebuild incrementally on Windows.

Bug: 40212971
Change-Id: I192a05e1b977e5442e8a8ecc06617938994880ef
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5893972
Reviewed-by: Hans Wennborg <hans@chromium.org>
Commit-Queue: danakj <danakj@chromium.org>
Reviewed-by: Łukasz Anforowicz <lukasza@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1361873}
NOKEYCHECK=True
GitOrigin-RevId: 4aa05521467cf5025f516d46138554673976371c

Author: danakj

build_rust.py

@@ -680,8 +680,28 @@ def main():
         'running specified command, skipping all normal build steps. For '
         'debugging. Running x.py directly will not set the appropriate env '
         'variables nor update config.toml')
+    if sys.platform == 'win32':
+        parser.add_argument('--sh', help='path to the sh.exe to use')
     args, rest = parser.parse_known_args()
 
+    if sys.platform == 'win32':
+        if args.sh:
+            assert args.sh.endswith('sh.exe')
+            p = os.environ['PATH']
+            shdir = os.path.dirname(args.sh)
+            os.environ['PATH'] = f'{shdir};{p}'
+        where = subprocess.check_output(['where.exe', 'sh'], text=True)
+        if '\\gnubby\\' in where.splitlines()[0]:
+            print("WARNING: It looks like you have gnubby sh.exe in your ")
+            print(" PATH, but it does not support normalized paths of the ")
+            print(" form `/c/foo` and will fail at the install step. Put the ")
+            print(" sh.exe from the Git installation into your PATH first ")
+            print(" when running this script or use --sh to specify the path ")
+            print(" to sh.exe.")
+            print("where sh.exe:")
+            print(where)
+            return 1
+
     debian_sysroot = None
     if sys.platform.startswith('linux') and not args.sync_for_gnrt:
         # Fetch sysroot we build rustc against. This ensures a minimum supported
@@ -691,7 +711,7 @@ def main():
 
     # Require zlib compression.
     if sys.platform == 'win32':
-        zlib_path = AddZlibToPath()
+        zlib_path = AddZlibToPath(dry_run=args.skip_checkout)
     else:
         zlib_path = None
 
@@ -701,9 +721,9 @@ def main():
     else:
         libxml2_dirs = None
 
-    # TODO(crbug.com/40205621): OpenSSL is somehow already present on the Windows
-    # builder, but we should change to using a package from 3pp when it is
-    # available.
+    # TODO(crbug.com/40205621): OpenSSL is somehow already present on the
+    # Windows builder, but we should change to using a package from 3pp when it
+    # is available.
     if (sys.platform != 'win32' and not args.sync_for_gnrt):
         # Building cargo depends on OpenSSL.
         AddOpenSSLToEnv()
@@ -806,8 +826,8 @@ def main():
     if args.prepare_run_xpy:
         return 0
 
-    building_on_host_triple = RustTargetTriple()
-    xpy_args = ['--build', building_on_host_triple]
+    target_triple = RustTargetTriple()
+    xpy_args = ['--build', target_triple]
 
     # Delete the build directory.
     if not args.skip_clean:
@@ -834,7 +854,7 @@ def main():
     if os.path.exists(RUST_TOOLCHAIN_OUT_DIR):
         RmTree(RUST_TOOLCHAIN_OUT_DIR)
 
-    xpy.run('install', [])
+    xpy.run('install', xpy_args + [])
 
     # The Rust stdlib deps are vendored to rust-src/library/vendor, and later
     # the x.py install process copies all subdirs of rust-src/library to the

config.toml.template

@@ -52,13 +52,13 @@ prefix = "$INSTALL_DIR"
 sysconfdir = "etc"
 
 [target.x86_64-pc-windows-msvc]
-llvm-config = "$LLVM_BIN/llvm-config"
+llvm-config = "$LLVM_BIN/llvm-config.exe"
 # TODO(danakj): We don't ship this in the clang toolchain package.
-# ranlib = "$LLVM_BIN/llvm-ranlib"
-ar = "$LLVM_BIN/llvm-lib"
-cc = "$LLVM_BIN/clang-cl"
-cxx = "$LLVM_BIN/clang-cl"
-linker = "$LLVM_BIN/lld-link"
+# ranlib = "$LLVM_BIN/llvm-ranlib.exe"
+ar = "$LLVM_BIN/llvm-lib.exe"
+cc = "$LLVM_BIN/clang-cl.exe"
+cxx = "$LLVM_BIN/clang-cl.exe"
+linker = "$LLVM_BIN/lld-link.exe"
 
 [target.aarch64-apple-darwin]
 llvm-config = "$LLVM_BIN/llvm-config"