Fix md5 comparisons

Author: shana

src/GitHub.Api/Installer/GitInstaller.cs

@@ -99,7 +99,7 @@ public bool IsGitLfsExtracted()
             var calculateMd5 = environment.FileSystem.CalculateMD5(GitLfsExecutablePath);
             logger.Trace("GitLFS MD5: {0}", calculateMd5);
             var md5 = environment.IsWindows ? WindowsGitLfsExecutableMD5 : MacGitLfsExecutableMD5;
-            if (calculateMd5 != md5)
+            if (String.Compare(calculateMd5, md5, true) != 0)
             {
                 logger.Trace("{0} has incorrect MD5", GitExecutablePath);
                 return false;

src/tests/IntegrationTests/Git/GitSetupTests.cs

@@ -42,7 +42,7 @@ public async Task InstallGit()
                 gitLfsDestinationPath.FileExists().Should().BeTrue();
 
                 var calculateMd5 = NPath.FileSystem.CalculateMD5(gitLfsDestinationPath);
-                GitInstaller.WindowsGitLfsExecutableMD5.Should().Be(calculateMd5);
+                Assert.IsTrue(string.Compare(calculateMd5, GitInstaller.WindowsGitLfsExecutableMD5, true) == 0);
 
                 setupDone = await gitSetup.SetupIfNeeded(new Progress<float>(x => percent = x));
                 setupDone.Should().BeFalse();