Skip source tests on Windows that depend on read-write bind-mounts

These were previously failing due to use of sh.exe on Windows, and with
that fixed, have been revealed to depend on bind-mounts.

Signed-off-by: Paul "TBBle" Hampson <Paul.Hampson@Pobox.com>

.github/workflows/windows.yaml

@@ -39,5 +39,5 @@ jobs:
       - name: Unit test
         env:
           SKIP_INTEGRATION_TESTS: 1
-        run: go test -mod=vendor -v ./frontend/dockerfile/... ./session/... ./util/...
+        run: go test -mod=vendor -v ./frontend/dockerfile/... ./session/... ./source/... ./util/...
         working-directory: src/github.com/moby/buildkit

source/git/gitsource_test.go

@@ -35,6 +35,10 @@ func TestRepeatedFetchKeepGitDir(t *testing.T) {
 }
 
 func testRepeatedFetch(t *testing.T, keepGitDir bool) {
+	if runtime.GOOS == "windows" {
+		t.Skip("Depends on unimplemented containerd bind-mount support on Windows")
+	}
+
 	t.Parallel()
 	ctx := context.TODO()
 
@@ -149,6 +153,10 @@ func TestFetchBySHAKeepGitDir(t *testing.T) {
 }
 
 func testFetchBySHA(t *testing.T, keepGitDir bool) {
+	if runtime.GOOS == "windows" {
+		t.Skip("Depends on unimplemented containerd bind-mount support on Windows")
+	}
+
 	t.Parallel()
 	ctx := namespaces.WithNamespace(context.Background(), "buildkit-test")
 
@@ -222,6 +230,10 @@ func TestMultipleReposKeepGitDir(t *testing.T) {
 }
 
 func testMultipleRepos(t *testing.T, keepGitDir bool) {
+	if runtime.GOOS == "windows" {
+		t.Skip("Depends on unimplemented containerd bind-mount support on Windows")
+	}
+
 	t.Parallel()
 	ctx := namespaces.WithNamespace(context.Background(), "buildkit-test")