Make PythonTests depend on the ExternalExecutable

This fixes builds on windows with fully-internal python
where the package is built but the exe isn't in instdir
when building a PythonTest.

Change-Id: Iab1d330a36adf1c849635b990bfe5d31359bec2b
Reviewed-on: https://gerrit.libreoffice.org/11618Reviewed-by: Matúš Kukan <matus.kukan@collabora.com>
Tested-by: Matúš Kukan <matus.kukan@collabora.com>

solenv/gbuild/PythonTest.mk

@@ -15,7 +15,7 @@ gb_PythonTest_EXECUTABLE_GDB := $(gb_Python_INSTALLED_EXECUTABLE_GDB)
 ifeq ($(OS),MACOSX)
 gb_PythonTest_DEPS := $(call gb_GeneratedPackage_get_target,python3)
 else
-gb_PythonTest_DEPS := $(call gb_Package_get_target,python3)
+gb_PythonTest_DEPS := $(call gb_ExternalExecutable_get_dependencies,python)
 endif
 gb_PythonTest_DEPS += $(if $(filter-out WNT,$(OS)),$(call gb_Package_get_target,python_shell))
 else