Auto merge of #98373 - joshtriplett:bootstrap-locking, r=jyn514

Move locking from bootstrap.py to rust bootstrap, using fd-lock

Helps with https://github.com/rust-lang/rust/issues/94829.

src/bootstrap/bootstrap.py

@@ -15,44 +15,6 @@ import tempfile
 
 from time import time, sleep
 
-# Acquire a lock on the build directory to make sure that
-# we don't cause a race condition while building
-# Lock is created in `build_dir/lock.db`
-def acquire_lock(build_dir):
-    try:
-        import sqlite3
-
-        path = os.path.join(build_dir, "lock.db")
-        try:
-            con = sqlite3.Connection(path, timeout=0)
-            curs = con.cursor()
-            curs.execute("BEGIN EXCLUSIVE")
-            # The lock is released when the cursor is dropped
-            return curs
-        # If the database is busy then lock has already been acquired
-        # so we wait for the lock.
-        # We retry every quarter second so that execution is passed back to python
-        # so that it can handle signals
-        except sqlite3.OperationalError:
-            del con
-            del curs
-            print("Waiting for lock on build directory")
-            con = sqlite3.Connection(path, timeout=0.25)
-            curs = con.cursor()
-            while True:
-                try:
-                    curs.execute("BEGIN EXCLUSIVE")
-                    break
-                except sqlite3.OperationalError:
-                    pass
-                sleep(0.25)
-            return curs
-    except ImportError:
-        print("warning: sqlite3 not available in python, skipping build directory lock")
-        print("please file an issue on rust-lang/rust")
-        print("this is not a problem for non-concurrent x.py invocations")
-        return None
-
 def support_xz():
     try:
         with tempfile.NamedTemporaryFile(delete=False) as temp_file:
@@ -928,11 +890,8 @@ def bootstrap(help_triggered):
 
     build.build = args.build or build.build_triple()
 
-    # Acquire the lock before doing any build actions
-    # The lock is released when `lock` is dropped
     if not os.path.exists(build.build_dir):
         os.makedirs(build.build_dir)
-    lock = acquire_lock(build.build_dir)
 
     # Fetch/build the bootstrap
     build.download_toolchain()