Use abs path to testing binary

Use the full path to the `functional.test.exe` binary when sharing into
the uVM for the `TestHVSock_*` test cases in
`test\functional\hvsock_test.go` to prevent vSMB share issues.

Otherwise, `os.Args[0]` will return the path that the tests were run
with (e.g., `.\functional.test.exe`), which can cause vSMB to fail with
`The parameter is incorrect.` (likely because it cannot find the current
file).

Signed-off-by: Hamza El-Saawy <hamzaelsaawy@microsoft.com>

test/functional/hvsock_test.go

@@ -22,6 +22,7 @@ import (
 	"golang.org/x/sys/windows"
 
 	hcsschema "github.com/Microsoft/hcsshim/internal/hcs/schema2"
+	"github.com/Microsoft/hcsshim/internal/uvm"
 	"github.com/Microsoft/hcsshim/osversion"
 
 	testcmd "github.com/Microsoft/hcsshim/test/internal/cmd"
@@ -134,8 +135,7 @@ func TestHVSock_UVM_HostBind(t *testing.T) {
 				return err
 			})
 
-			guestPath := filepath.Join(`C:\`, filepath.Base(os.Args[0]))
-			testuvm.Share(ctx, t, vm, os.Args[0], guestPath, true)
+			guestPath := share_self(ctx, t, vm, "")
 
 			reexecCmd := fmt.Sprintf(`%s -test.run=%s`, guestPath, util.TestNameRegex(t))
 			if testing.Verbose() {
@@ -231,8 +231,7 @@ func TestHVSock_UVM_GuestBind(t *testing.T) {
 			ctx, cancel := context.WithTimeout(ctx, hvsockTestTimeout) //nolint:govet // ctx is shadowed
 			t.Cleanup(cancel)
 
-			guestPath := filepath.Join(`C:\`, filepath.Base(os.Args[0]))
-			testuvm.Share(ctx, t, vm, os.Args[0], guestPath, true)
+			guestPath := share_self(ctx, t, vm, "")
 
 			reexecCmd := fmt.Sprintf(`%s -test.run=%s`, guestPath, util.TestNameRegex(t))
 			if testing.Verbose() {
@@ -1148,3 +1147,22 @@ func goBlockT[T any](f func() T) <-chan T {
 
 	return ch
 }
+
+func share_self(ctx context.Context, tb testing.TB, vm *uvm.UtilityVM, base string) string {
+	tb.Helper()
+
+	if base == "" {
+		base = `C:\`
+	}
+
+	// use [os.Executable] over `os.Args[0]` to make sure path is absolute
+	self, err := os.Executable()
+	if err != nil {
+		tb.Fatalf("get testing binary path: %v", err)
+	}
+
+	guestPath := filepath.Join(base, filepath.Base(self))
+	testuvm.Share(ctx, tb, vm, self, guestPath, true)
+
+	return guestPath
+}