[6.2] test/CMakeLists.txt: run Embedded Swift for Wasm tests (#83287)

Cherry-pick of #83128, #82399, and #82878, merged as ea6ca2b5db, 0c4e56174b, and e34eb3331f respectively.

**Explanation**: Currently `test/CMakeLists.txt` can only set `SWIFT_LIT_ARGS` for all tests uniformly. This means that we can't have tests for Embedded Swift with a different set of `lit.py` arguments.

Also, create new `check-swift-embedded-wasi` target from `test/CMakeLists.txt`, tweak `lit.cfg` to support WASI Clang resource dir, exclude unsupported tests based on `CPU=wasm32` instead of `OS=wasi`.

**Scope**: Limited to Embedded Swift test suite.
**Risk**: Low, due to limited scope.
**Testing**: #82878 was incubated on `main` for 2 weeks, #82399 for 3 weeks with no disruption, #83128 merged this week, but enables all these tests on CI, which are consistently passing.
**Issue**: rdar://156585717
**Reviewer**: @bnbarham

utils/swift_build_support/swift_build_support/products/wasmstdlib.py

@@ -184,6 +184,7 @@ class WasmStdlib(cmake_product.CMakeProduct):
             self.build_dir, 'test-wasi-wasm32', path) for path in lit_test_paths]
         self.cmake_options.define('SWIFT_LIT_TEST_PATHS:STRING',
                                   ';'.join(lit_test_paths))
+        self.cmake_options.define('LLVM_LIT_ARGS', self.args.lit_args)
         test_driver_options = [
             # compiler-rt is not installed in the final toolchain, so use one
             # in build dir
@@ -201,6 +202,9 @@ class WasmStdlib(cmake_product.CMakeProduct):
         self.cmake_options.define('SWIFT_THREADING_PACKAGE:STRING', 'none')
 
     def test(self, host_target):
+        self._test(host_target, 'wasm32-wasip1')
+
+    def _test(self, host_target, target_triple):
         build_root = os.path.dirname(self.build_dir)
         bin_paths = [
             os.path.join(self._host_swift_build_dir(host_target), 'bin'),
@@ -222,7 +226,14 @@ class WasmStdlib(cmake_product.CMakeProduct):
             'LIT_FILTER_OUT':
                 '(Concurrency/Runtime/clock.swift|stdlib/StringIndex.swift)',
         }
-        self.test_with_cmake(None, [test_target], self._build_variant, [], test_env=env)
+
+        # Embedded stdlib is not built for the threads triple, don't include embedded tests for it.
+        if target_triple == 'wasm32-wasip1-threads':
+            test_targets = [test_target]
+        else:
+            test_targets = [test_target, 'check-swift-embedded-wasi']
+
+        self.test_with_cmake(None, test_targets, self._build_variant, [], test_env=env)
 
     def should_test_executable(self):
         return True
@@ -259,6 +270,9 @@ class WasmThreadsStdlib(WasmStdlib):
     def build(self, host_target):
         self._build(host_target, 'wasm32-wasip1-threads', 'wasip1-threads-wasm32')
 
+    def test(self, host_target):
+        self._test(host_target, 'wasm32-wasip1-threads')
+
     def should_test_executable(self):
         # TODO(katei): Enable tests once WasmKit supports WASI threads
         return False