Add build script to compile bash dynamically

[vidyalakshmir]

Description

This PR introduces a dynamic (shared) WebAssembly build script for Bash.

Key Changes

• Enabled Position Independent Code (PIC): Appended -fPIC to CFLAGS so all core objects and builtins are compiled for dynamic linking.
• Updated WASM Linker Flags: Replaced static memory bounds with dynamic PIE flags (-Wl,-pie, -Wl,--import-table, -Wl,--export-dynamic, -Wl,--experimental-pic).
• Restored libdl Support: Re-introduced -ldl in the final linker command to support loading shared objects at runtime.
• Automated LindFS Installation: Added a final step that automatically copies the compiled bash binary (and .cwasm if available) directly into $LINDFS_ROOT/bin.

Integration with lind-wasm branch dylink_impl_integration

The latest dylink_impl_integration of lind-wasm is used. Steps followed are detailed below.

git checkout dylink_impl_integration
git pull
make
scripts/make_shared_glibc.sh
scripts/make_shared_libm.sh
cd src/lind-boot
cargo build --features disable_signals

Updated lind-wasm/scripts/append_tls_relocs_export.sh to use standard wasm2wat and wat2wasm commands instead of absolute paths.

Tested

Test script

Tested with a simple test script lind-wasm/lindfs/bash_tests/test.sh

#!/bin/bash
name="Bash"
if [[ -n "$name" ]]; then
  printf "Hello, %s!\n" "$name"
fi
for i in {1..3}; do
  printf "Count: %d\n" "$i"
done

Command to run the test

sudo /home/lind/lind-wasm/src/lind-boot/target/debug/lind-boot --preload env=lib/libc.so bin/bash.wasm tests/bash/test.sh

This causes the following error:

thread 'main' (575449) panicked at /home/lind/lind-wasm/src/wasmtime/crates/environ/src/vmoffsets.rs:784:9:
assertion failed: index.as_u32() < self.num_defined_memories
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

Previous run

sudo /home/lind/lind-wasm/src/lind-boot/target/debug/lind-boot --preload env=/lib/libc.so --preload env=/lib/libm.so /bin/bash /bash_tests/test.sh

Error

thread 'main' (48837) panicked at src/lind_wasmtime/execute.rs:726:33:
called `Option::unwrap()` on a `None` value
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

How it was resolved

This error got resolved when the first '/' was removed from the paths within lindfs. So /lib/libc.so was changed to lib/libc.so

[vidyalakshmir]

I am adding this PR to get started with compiling apps for dynamic loading. I have mentioned the steps followed to use the new 'dynamic loading' branch within lind-wasm. Also the steps to build bash dynamically was followed looking at the python build scripts from 'build_python' branch of lind-wasm-apps/.

I am hitting an issue when I run both bash and python which is built for dynamic loading. @qianxichen233

[rennergade]

this is a static build thing. is libc not dynamic now?

[rennergade]

probably want to remove this since we'll have our own make install

[vidyalakshmir]

As of now, the earlier error while running bash and python has been resolved. This was mainly because of the way in which paths was passed as argument to Lind-boot. For example, lindfs/lib/libc.so should be passed as lib/lib.so

Now I hit a different error

thread 'main' (575449) panicked at /home/lind/lind-wasm/src/wasmtime/crates/environ/src/vmoffsets.rs:784:9:
assertion failed: index.as_u32() < self.num_defined_memories
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace