test: Add basic code coverage script

For now it only tests the wasi-fyi tests.

Needs to be extended with all the other tests.

scripts/code-coverage.sh

@@ -0,0 +1,33 @@
+#!/usr/bin/env bash
+
+set -Eeuxo pipefail
+
+DIR="$( cd "$( dirname "${BASH_SOURCE[0]}" )" && pwd )"
+# get absolute path of the root dir
+ROOT_DIR="$( cd "${DIR}/.." && pwd )"
+
+export CARGO_TARGET_DIR="$ROOT_DIR/target/llvm-cov"
+
+# Set the environment variables needed to get coverage.
+source <(cargo llvm-cov show-env --export-prefix)
+
+# Remove artifacts that may affect the coverage results.
+# This command should be called after show-env.
+# cargo llvm-cov clean --workspace
+# Above two commands should be called before build binaries.
+
+ # Build rust binaries.
+cargo build --locked -p wasmer-cli -F singlepass,cranelift --release
+
+# cargo-llvm-cov expects the debug binaries to be in /debug.
+# We compile with --release because otherwise running is way too slow.
+# So we copy the release binaries to /debug, which makes things work.
+rm -rf "$CARGO_TARGET_DIR/debug"
+cp -r "$CARGO_TARGET_DIR/release" "$CARGO_TARGET_DIR/debug"
+
+# Commands using binaries in target/, including `cargo test` and other cargo subcommands.
+
+TEST_RUNNER="$CARGO_TARGET_DIR/release/wasmer" $ROOT_DIR/tests/wasi-fyi/test.sh
+
+# Generate reports.
+cargo llvm-cov report --html