fix linux tests

Author: Lance Parker

validation-test/stdlib/String.swift

@@ -2199,8 +2199,8 @@ for test in comparisonTestCases {
   }
 
   StringTests.test("Comparison.OpaqueSubstring.\(test.strings)")
-    .skip(.linuxAny(reason: "NSSlowString requires ObjC interop"))
-    .code {
+  .skip(.linuxAny(reason: "NSSlowString requires ObjC interop"))
+  .code {
     test.testOpaqueSubstrings()
   }
 }
@@ -2220,24 +2220,17 @@ StringTests.test("NormalizationCheck") {
   expectEqual(expectedCodeUnits, nfcCodeUnits)
 }
 
-StringTests.test("NormalizationCheck/Opaque") {
+StringTests.test("NormalizationCheck/Opaque")
+.skip(.linuxAny(reason: "NSSlowString requires ObjC interop"))
+.code {
+#if _runtime(_ObjC)
   let str = "\u{0336}\u{0344}\u{0357}\u{0343}\u{0314}\u{0351}\u{0340}\u{0300}\u{0340}\u{0360}\u{0314}\u{0357}\u{0315}\u{0301}\u{0344}a"
   let opaqueString = NSSlowString(string: str) as String
   let nfcCodeUnits = opaqueString._nfcCodeUnits
   let expectedCodeUnits: [UInt8] = [0xCC, 0xB6, 0xCC, 0x88, 0xCC, 0x81, 0xCD, 0x97, 0xCC, 0x93, 0xCC, 0x94, 0xCD, 0x91, 0xCC, 0x80, 0xCC, 0x80, 0xCC, 0x80, 0xCC, 0x94, 0xCD, 0x97, 0xCC, 0x81, 0xCC, 0x88, 0xCC, 0x81, 0xCC, 0x95, 0xCD, 0xA0, 0x61]
 
   expectEqual(expectedCodeUnits, nfcCodeUnits)
-}
-
-StringTests.test("ABC") {
-  let str = "abcdefg"
-  let nfcCodeUnits = str._nfcCodeUnits
-  let expectedCodeUnits = Array(str.utf8)
-  
-  expectEqual(expectedCodeUnits, nfcCodeUnits)
-  
-  let opaqueString = NSSlowString(string: str) as String
-  expectEqual(expectedCodeUnits, opaqueString._nfcCodeUnits)
+#endif
 }
 
 runAllTests()