Use "realpath" when creating test file to test tests

Now that we call "realpath" when loading files, we should get the
expected output on systems like macOS where the temporary directory is
a symlink.

Author: d-torrance

M2/Macaulay2/tests/normal/testing.m2

@@ -1,8 +1,9 @@
-testpkg = minimizeFilename(temporaryFileName() | ".m2")
+testpkg = temporaryFileName() | ".m2"
 testpkg << ///newPackage("TestPackage")
 beginDocumentation()
 TEST "assert Equation(1 + 1, 2)"
 /// << close
+testpkg = minimizeFilename realpath testpkg
 loadPackage("TestPackage", FileName => testpkg)
 check "TestPackage"
 pkgtest = tests(0, "TestPackage")