Optimize more aggressively for WASM builds

Use `-Oz` instead of `-Os` because why not, and include LLVM
bitcode in C dependencies.

This reduces `liblightningjs_release.wasm` from 3.0MB to 2.4MB,
likely mostly from removing secp256k1 symbols that were unused.

diff --git a/genbindings.sh b/genbindings.sh
index 17522868857589700921f4d4a49fecae31b58a05..edaa01d50de3b871a219fd637e2115653e649bae 100755 (executable)
--- a/genbindings.sh
+++ b/genbindings.sh
@@ -485,10 +485,10 @@ if [ "$2" = "false" -a "$(rustc --print target-list | grep wasm32-wasi)" != "" ]
        echo "int main() {}" > genbindings_wasm_test_file.c
        if clang -nostdlib -o /dev/null --target=wasm32-wasi -Wl,--no-entry genbindings_wasm_test_file.c > /dev/null 2>&1; then
                # And if it does, build a WASM binary without capturing errors
-               export CFLAGS_wasm32_wasi="$BASE_CFLAGS -target wasm32"
+               export CFLAGS_wasm32_wasi="$BASE_CFLAGS -target wasm32 -O1"
                RUSTFLAGS="$RUSTFLAGS --cfg=test_mod_pointers" cargo rustc $CARGO_BUILD_ARGS -v --target=wasm32-wasi
-               export CFLAGS_wasm32_wasi="$BASE_CFLAGS -target wasm32 -Os"
-               CARGO_PROFILE_RELEASE_LTO=true cargo rustc $CARGO_BUILD_ARGS -v --release --target=wasm32-wasi -- -C embed-bitcode=yes -C opt-level=s -C linker-plugin-lto -C lto
+               export CFLAGS_wasm32_wasi="$BASE_CFLAGS -fembed-bitcode -target wasm32 -Oz"
+               CARGO_PROFILE_RELEASE_LTO=true cargo rustc $CARGO_BUILD_ARGS -v --release --target=wasm32-wasi -- -C embed-bitcode=yes -C opt-level=z -C linker-plugin-lto -C lto
        else
                echo "Cannot build WASM lib as clang does not seem to support the wasm32-wasi target"
        fi