Feature-gate test-programs

This commit feature-gates `test-programs` as a workaround for
`cargo test` not allowing for optional dev-dependencies.

This commit addresses #595.

crates/test-programs/build.rs

@@ -3,16 +3,19 @@
 //! By generating a separate `#[test]` test for each file, we allow cargo test
 //! to automatically run the files in parallel.
 
+fn main() {
+    #[cfg(features = "test-programs")]
+    wasi_tests::build_and_generate_tests()
+}
+
+#[cfg(features = "test-programs")]
+mod wasi_tests {
     use std::env;
     use std::fs::{read_dir, DirEntry, File};
     use std::io::{self, Write};
     use std::path::{Path, PathBuf};
     use std::process::{Command, Stdio};
 
-fn main() {
-    build_and_generate_tests()
-}
-
     fn build_and_generate_tests() {
         // Validate if any of test sources are present and if they changed
         // This should always work since there is no submodule to init anymore
@@ -28,8 +31,9 @@ fn build_and_generate_tests() {
             }
         }
         // Build tests to OUT_DIR (target/*/build/wasi-common-*/out/wasm32-wasi/release/*.wasm)
-    let out_dir =
+        let out_dir = PathBuf::from(
-        PathBuf::from(env::var("OUT_DIR").expect("The OUT_DIR environment variable must be set"));
+            env::var("OUT_DIR").expect("The OUT_DIR environment variable must be set"),
+        );
         let mut out =
             File::create(out_dir.join("wasi_tests.rs")).expect("error generating test source file");
         build_tests("wasi-tests", &out_dir).expect("building tests");
@@ -104,7 +108,11 @@ fn test_directory(out: &mut File, testsuite: &str, out_dir: &Path) -> io::Result
         Ok(())
     }
 
-fn write_testsuite_tests(out: &mut File, dir_entry: DirEntry, testsuite: &str) -> io::Result<()> {
+    fn write_testsuite_tests(
+        out: &mut File,
+        dir_entry: DirEntry,
+        testsuite: &str,
+    ) -> io::Result<()> {
         let path = dir_entry.path();
         let stemstr = path
             .file_stem()
@@ -191,3 +199,4 @@ fn no_preopens(testsuite: &str, name: &str) -> bool {
             unreachable!()
         }
     }
+}

crates/test-programs/tests/wasm_tests/main.rs

@@ -1,3 +1,4 @@
+#![cfg(features = "test-programs")]
 mod runtime;
 mod utils;