as an alternative to passing the link-args using the environmental variable,
we can also use build script to pass the "-C link-args=<FLAG>" to the compiler.
see https://doc.rust-lang.org/nightly/cargo/reference/build-scripts.html#cargorustc-link-argflag
to ensure that cargo is called again by ninja, after build.rs is
updated, build.rs is added as a dependency of {wasm} files along with
Cargo.lock.
this change is verified using following command
```
RUSTFLAGS='--print link-args' cargo build \
--target=wasm32-wasi \
--example=return_input \
--locked \
--manifest-path=Cargo.toml \
--target-dir=build/cmake/test/resource/wasm/rust
```
the output includes "-zstack-size=131072" in the argument passed to lld:
```
Compiling examples v0.0.0 (/home/kefu/dev/scylladb/test/resource/wasm/rust)
LC_ALL="C"
PATH="/usr/lib/rustlib/x86_64-unknown-linux-gnu/bin:/usr/lib/rustlib/x86_64-unknown-linux-gnu/bin/self-contained:/home/kefu/.local/bin:/home/kefu/bin:/usr/local/bin:/usr/local/sbin:/usr/bin:/usr/sbin"
VSLANG="1033"
"lld"
"-flavor" "wasm" "--rsp-quoting=posix" "--export"
"_scylla_abi" "--export" "_scylla_free" "--export" "_scylla_malloc"
"--export" "return_input" "-z" "stack-size=1048576" "--stack-first"
"--allow-undefined" "--fatal-warnings" "--no-demangle"
...
"-L" "/usr/lib/rustlib/wasm32-wasi/lib"
"-L" "/usr/lib/rustlib/wasm32-wasi/lib/self-contained"
"-o"
"/home/kefu/dev/scylladb/build/cmake/test/resource/wasm/rust/wasm32-wasi/debug/examples/return_input-ef03083560989040.wasm"
"--gc-sections"
"--no-entry"
"-O0"
"-zstack-size=131072"
```
with this change, it'd be easier to build .wat files in CMake, so
we don't need to repeat the settings in both configure.py and
CMakeLists.txt
Signed-off-by: Kefu Chai <kefu.chai@scylladb.com>
Closes#14123
9ba610c811