build-script: allow --test-wasm-stdlib without --build-wasm-stdlib

This allows testing Wasm stdlib without rebuilding WASI sysroot and stdlib, while some changes are still detected by ninja as dependencies and are rebuilt, which is great for local incremental builds.

Author: MaxDesiatov

utils/build_swift/build_swift/driver_arguments.py

@@ -829,6 +829,8 @@ def create_argument_parser():
     option(['--build-wasm-stdlib'], toggle_true('build_wasmstdlib'),
            help='build the stdlib for WebAssembly target into a'
                 'separate build directory ')
+    option('--test-wasm-stdlib', toggle_true('test_wasmstdlib'),
+           help='test stdlib for WebAssembly')
     option(['--wasmkit'], toggle_true('build_wasmkit'),
            help='build WasmKit')
     option(['--install-wasmkit'], toggle_true('install_wasmkit'),

utils/swift_build_support/swift_build_support/build_script_invocation.py

@@ -683,7 +683,7 @@ def compute_product_pipelines(self):
         builder.add_product(products.WasmKit,
                             is_enabled=self.args.build_wasmkit)
         builder.add_product(products.WasmStdlib,
-                            is_enabled=self.args.build_wasmstdlib)
+                            is_enabled=self.args.build_wasmstdlib or self.args.test_wasmstdlib)
         builder.add_product(products.WasmThreadsStdlib,
                             is_enabled=self.args.build_wasmstdlib)
         builder.add_product(products.WasmSwiftSDK,