vulkan: Fix gen_enum_to_str in out of tree builds

In some configurations the util directory is created when building out
of tree, but not others. This patch ensures that it's created.

Signed-off-by: Dylan Baker <dylanx.c.baker@intel.com>
Reviewed-by: Matt Turner <mattst88@gmail.com>
Reviewed-and-Tested-by: Mike Lothian <mike@fireburn.co.uk>

src/vulkan/Makefile.am

@@ -5,6 +5,9 @@ noinst_LTLIBRARIES = libvulkan_wsi.la libvulkan_util.la
 vulkan_includedir = $(includedir)/vulkan
 vulkan_api_xml = $(top_srcdir)/src/vulkan/registry/vk.xml
 
+MKDIR_GEN = $(AM_V_at)$(MKDIR_P) $(@D)
+PYTHON_GEN = $(AM_V_GEN)$(PYTHON2) $(PYTHON_FLAGS)
+
 EXTRA_DIST = \
 	util/gen_enum_to_str.py
 
@@ -13,7 +16,8 @@ BUILT_SOURCES = \
 	util/vk_enum_to_str.h
 
 util/vk_enum_to_str.c util/vk_enum_to_str.h: util/gen_enum_to_str.py $(vulkan_api_xml)
-	$(AM_V_GEN)$(PYTHON2) $(srcdir)/util/gen_enum_to_str.py
+	$(MKDIR_GEN)
+	$(PYTHON_GEN) $(srcdir)/util/gen_enum_to_str.py
 
 libvulkan_util_la_SOURCES = $(VULKAN_UTIL_FILES)