[android] Fix URL tests that use hardcoded /tmp

In Android /tmp doesn't exist, and the temporary directory is normally
/data/local/tmp. It is not a symlink. The tests were mostly working, but
because `resolvingSymlinksInPath` returns a trailing slash if the
directory actually exists, in Android it was returning without the final
trailing slash in some of the cases.

The changes use the value of `NSTemporaryDirectory` in Android only, and
also uses that value for the expected value. Using an existing directory
matches the tests from Darwin/Linux. I didn't want to use
`NSTemporaryDirectory` in every platform because at least in Darwin I
get a value which is not neither /tmp nor /private/tmp.

Author: drodriguez

TestFoundation/TestURL.swift

@@ -394,11 +394,20 @@ class TestURL : XCTestCase {
         }
 
         // tmp is special because it is symlinked to /private/tmp and this /private prefix should be dropped,
-        // so tmp is tmp. On Linux tmp is not symlinked so it would be the same.
+        // so tmp is tmp. On Linux tmp is not symlinked so it would be the same. In Android it doesn't exist
+        // so we have to use NSTemporaryDirectory to be safe.
+        #if !os(Android)
+        let tmpDirectoryPath = "/tmp"
+        let expectedTmpURLPrefix = "file:///tmp"
+        #else
+        // We don't want the trailing slash to match other platforms
+        let tmpDirectoryPath = NSTemporaryDirectory().dropLast(1)
+        let expectedTmpURLPrefix = "file://\(NSTemporaryDirectory())".dropLast(1)
+        #endif
         do {
-            let url = URL(fileURLWithPath: "/.//tmp/ABC/..")
+            let url = URL(fileURLWithPath: "/./\(tmpDirectoryPath)/ABC/..")
             let result = url.resolvingSymlinksInPath().absoluteString
-            XCTAssertEqual(result, "file:///tmp/", "URLByResolvingSymlinksInPath removes extraneous path components and resolve symlinks.")
+            XCTAssertEqual(result, "\(expectedTmpURLPrefix)/", "URLByResolvingSymlinksInPath removes extraneous path components and resolve symlinks.")
         }
 
         do {
@@ -418,22 +427,22 @@ class TestURL : XCTestCase {
         // tmp is symlinked on macOS only
         #if os(macOS)
         do {
-            let url = URL(fileURLWithPath: "/tmp/..")
+            let url = URL(fileURLWithPath: "\(tmpDirectoryPath)/..")
             let result = url.resolvingSymlinksInPath().absoluteString
             XCTAssertEqual(result, "file:///private/")
         }
         #else
         do {
-            let url = URL(fileURLWithPath: "/tmp/ABC/test_URLByResolvingSymlinksInPath")
+            let url = URL(fileURLWithPath: "\(tmpDirectoryPath)/ABC/test_URLByResolvingSymlinksInPath")
             let result = url.resolvingSymlinksInPath().absoluteString
-            XCTAssertEqual(result, "file:///tmp/ABC/test_URLByResolvingSymlinksInPath", "URLByResolvingSymlinksInPath appends trailing slash for existing directories only")
+            XCTAssertEqual(result, "\(expectedTmpURLPrefix)/ABC/test_URLByResolvingSymlinksInPath", "URLByResolvingSymlinksInPath appends trailing slash for existing directories only")
         }
         #endif
 
         do {
-            let url = URL(fileURLWithPath: "/tmp/ABC/..")
+            let url = URL(fileURLWithPath: "\(tmpDirectoryPath)/ABC/..")
             let result = url.resolvingSymlinksInPath().absoluteString
-            XCTAssertEqual(result, "file:///tmp/")
+            XCTAssertEqual(result, "\(expectedTmpURLPrefix)/")
         }
     }