Merge pull request #3145 from Xazax-hun/expose-not-cxx

Test new @_expose(!Cxx) attribute syntax

Author: Xazax-hun

Tests/SwiftParserTest/AttributeTests.swift

@@ -579,6 +579,12 @@ final class AttributeTests: ParserTestCase {
       """
     )
 
+    assertParse(
+      """
+      @_expose(!Cxx) func foo() {}
+      """
+    )
+
     assertParse(
       """
       @_expose(Cxx, "baz") func foo() {}