Skip some tests on Linux due to the behavior differences (abount description) of some Foundation types

Author: ikesyo

Tests/NimbleTests/Matchers/BeEmptyTest.swift

@@ -51,12 +51,14 @@ final class BeEmptyTest: XCTestCase, XCTestCaseProvider {
             expect([1]).to(beEmpty())
         }
 
+#if os(macOS) || os(iOS) || os(tvOS) || os(watchOS)
         failsWithErrorMessage("expected to not be empty, got <{()}>") {
             expect(NSSet()).toNot(beEmpty())
         }
         failsWithErrorMessage("expected to be empty, got <{(1)}>") {
             expect(NSSet(object: NSNumber(value: 1))).to(beEmpty())
         }
+#endif
 
         failsWithErrorMessage("expected to not be empty, got <()>") {
             expect(NSIndexSet()).toNot(beEmpty())

Tests/NimbleTests/Matchers/MatchErrorTest.swift

@@ -19,10 +19,12 @@ final class MatchErrorTest: XCTestCase, XCTestCaseProvider {
     }
 
     func testMatchNSErrorPositive() {
+#if os(macOS) || os(iOS) || os(tvOS) || os(watchOS)
         let error1 = NSError(domain: "err", code: 0, userInfo: nil)
         let error2 = NSError(domain: "err", code: 0, userInfo: nil)
 
         expect(error1).to(matchError(error2))
+#endif
     }
 
     func testMatchNSErrorNegative() {
@@ -43,11 +45,13 @@ final class MatchErrorTest: XCTestCase, XCTestCaseProvider {
             expect(CustomDebugStringConvertibleError.a).to(matchError(CustomDebugStringConvertibleError.b))
         }
 
+#if os(macOS) || os(iOS) || os(tvOS) || os(watchOS)
         failsWithErrorMessage("expected to match error <Error Domain=err Code=1 \"(null)\">, got <Error Domain=err Code=0 \"(null)\">") {
             let error1 = NSError(domain: "err", code: 0, userInfo: nil)
             let error2 = NSError(domain: "err", code: 1, userInfo: nil)
             expect(error1).to(matchError(error2))
         }
+#endif
     }
 
     func testMatchNegativeMessage() {