Fix macos-arm64 CI. NFC (#19658)

We were previously using EMTEST_SKIP_SIMD to skip simd tests due to
lack of native clang, but since we updated node to v16
`EMTEST_SKIP_SIMD` is not even checked.

Instead use `EMTEST_LACKS_NATIVE_CLANG` to skip the tests that depend on
this.

Author: sbc100

.circleci/config.yml

@@ -723,7 +723,6 @@ jobs:
       EMTEST_SKIP_V8: "1"
       EMTEST_SKIP_EH: "1"
       EMTEST_SKIP_WASM64: "1"
-      EMTEST_SKIP_SIMD: "1"
       EMTEST_SKIP_SCONS: "1"
       EMCC_SKIP_SANITY_CHECK: "1"
     steps:
@@ -752,8 +751,9 @@ jobs:
       EMTEST_SKIP_V8: "1"
       EMTEST_SKIP_EH: "1"
       EMTEST_SKIP_WASM64: "1"
-      EMTEST_SKIP_SIMD: "1"
       EMTEST_SKIP_SCONS: "1"
+      # Some native clang tests assume x86 clang (e.g. -sse2)
+      EMTEST_LACKS_NATIVE_CLANG: "1"
       EMCC_SKIP_SANITY_CHECK: "1"
     steps:
       - setup-macos