pkg/archive: adjust chmod bits on windows

This change modifies the chmod bits of build context archives built on
windows to preserve the execute bit and remove the r/w bits from
grp/others.

Also adjusted integ-cli tests to verify permissions based on the platform
the tests are running.

Fixes #11047.

Signed-off-by: Ahmet Alp Balkan <ahmetalpbalkan@gmail.com>

archive/archive_unix_test.go

@@ -3,6 +3,7 @@
 package archive
 
 import (
+	"os"
 	"testing"
 )
 
@@ -40,3 +41,20 @@ func TestCanonicalTarName(t *testing.T) {
 		}
 	}
 }
+
+func TestChmodTarEntry(t *testing.T) {
+	cases := []struct {
+		in, expected os.FileMode
+	}{
+		{0000, 0000},
+		{0777, 0777},
+		{0644, 0644},
+		{0755, 0755},
+		{0444, 0444},
+	}
+	for _, v := range cases {
+		if out := chmodTarEntry(v.in); out != v.expected {
+			t.Fatalf("wrong chmod. expected:%v got:%v", v.expected, out)
+		}
+	}
+}