Work around CGFloat(native: ...) description on Linux

This should be removed once we get the following: swiftlang/swift-corelibs-foundation#585

Author: ikesyo

Tests/NimbleTests/Matchers/BeCloseToTest.swift

@@ -52,7 +52,13 @@ final class BeCloseToTest: XCTestCase, XCTestCaseProvider {
         expect(CGFloat(1.2)).to(beCloseTo(1.2001))
         expect(CGFloat(1.2)).to(beCloseTo(CGFloat(1.2001)))
 
-        failsWithErrorMessage("expected to be close to <1.2001> (within 1), got <1.2>") {
+        let got: String
+        #if _runtime(_ObjC)
+            got = "1.2"
+        #else
+            got = "CGFloat(native: 1.2)"
+        #endif
+        failsWithErrorMessage("expected to be close to <1.2001> (within 1), got <\(got)>") {
             expect(CGFloat(1.2)).to(beCloseTo(1.2001, within: 1.0))
         }
     }