login,build: skip /dev/fd and /dev/std{in,out,err} binds when host already has them

Partial fix for #689

Author: sylirre

proot_distro/commands/login/proot_cmd.py

@@ -185,12 +185,11 @@ def _add_non_minimal_binds(
 
 def _add_termux_dev_binds(args, rootfs):
     """Bind device files and fake /proc/sys substitutes used by Termux."""
-    args += [
-        "--bind=/dev/urandom:/dev/random",
-        "--bind=/proc/self/fd:/dev/fd",
-    ]
+    args.append("--bind=/dev/urandom:/dev/random")
+    if not os.path.lexists("/dev/fd"):
+        args.append("--bind=/proc/self/fd:/dev/fd")
     for i, name in ((0, "stdin"), (1, "stdout"), (2, "stderr")):
-        if os.path.exists(f"/proc/self/fd/{i}"):
+        if not os.path.lexists(f"/dev/{name}") and os.path.exists(f"/proc/self/fd/{i}"):
             args.append(f"--bind=/proc/self/fd/{i}:/dev/{name}")
     sysdata_dir = os.path.join(os.path.dirname(rootfs), "sysdata")
     args.append(f"--bind={sysdata_dir}/sys_empty:/sys/fs/selinux")

proot_distro/helpers/build_engine/run_step.py

@@ -174,12 +174,11 @@ def _exec_proot(engine, stage, command, stdin_input):
     proot_args += ["--bind=/dev", "--bind=/proc", "--bind=/sys"]
 
     if IS_TERMUX:
-        proot_args += [
-            "--bind=/dev/urandom:/dev/random",
-            "--bind=/proc/self/fd:/dev/fd",
-        ]
+        proot_args.append("--bind=/dev/urandom:/dev/random")
+        if not os.path.lexists("/dev/fd"):
+            proot_args.append("--bind=/proc/self/fd:/dev/fd")
         for i, name in ((0, "stdin"), (1, "stdout"), (2, "stderr")):
-            if os.path.exists(f"/proc/self/fd/{i}"):
+            if not os.path.lexists(f"/dev/{name}") and os.path.exists(f"/proc/self/fd/{i}"):
                 proot_args.append(f"--bind=/proc/self/fd/{i}:/dev/{name}")
         setup_fake_sysdata(rootfs)
         sysdata_dir = os.path.join(os.path.dirname(rootfs), "sysdata")