node_cache: Work around pnpm install issue in Docker for Mac.

On Docker for Mac with the gRPC FUSE or VirtioFS file sharing
implementations, we nondeterministically get errors like this from
pnpm install:

    pnpm: ENOENT: no such file or directory, copyfile '/srv/zulip/.pnpm-store/v3/files/7d/6b44bb658625281b48194e5a3d3a07452bea1f256506dd16f7a21941ef3f0d259e1bcd0cc6202642bf1fd129bc187e6a3921d382d568d312bd83f3023979a0' -> '/srv/zulip/node_modules/.pnpm/regexpu-core@5.3.2/node_modules/_tmp_3227_7f867a9c510832f5f82601784e21e7be/LICENSE-MIT.txt'

    Subcommand of ./lib/provision.py failed with exit status 1: /usr/local/bin/pnpm install --frozen-lockfile
    Actual error output for the subcommand is just above this.

Work around this using --package-import-method=copy.

Signed-off-by: Anders Kaseorg <anders@zulip.com>

scripts/lib/node_cache.py

@@ -1,6 +1,6 @@
 import os
 
-from scripts.lib.zulip_tools import run
+from scripts.lib.zulip_tools import get_deploy_root, run
 
 DEFAULT_PRODUCTION = False
 
@@ -16,11 +16,16 @@ def setup_node_modules(production: bool = DEFAULT_PRODUCTION) -> None:
     except FileNotFoundError:
         pass
 
-    run(
-        [
-            "/usr/local/bin/pnpm",
-            "install",
-            "--frozen-lockfile",
-            *(["--prod"] if production else []),
-        ]
-    )
+    pnpm_command = ["/usr/local/bin/pnpm", "install", "--frozen-lockfile"]
+    if production:
+        pnpm_command += ["--prod"]
+
+    deploy_root = get_deploy_root()
+    with open("/proc/self/mounts") as mounts:
+        for line in mounts:
+            fields = line.split()
+            if fields[1] == deploy_root and fields[2] in ("fuse.grpcfuse", "fakeowner"):
+                print("Working around https://github.com/pnpm/pnpm/issues/5803")
+                pnpm_command += ["--package-import-method=copy"]
+
+    run(pnpm_command)