fix build: use same conditional as in configure

Change-Id: I2383baaafbb5f79e1469a6296f3d65f1eadfa5eb
diff --git a/RepositoryExternal.mk b/RepositoryExternal.mk
index cad1db6..4fba2a4 100644
--- a/RepositoryExternal.mk
+++ b/RepositoryExternal.mk
@@ -3469,7 +3469,7 @@ $(call gb_LinkTarget_add_libs,$(1),\

endef

else # NON-SYSTEM_GPGME
else ifneq ($(filter GPGMEPP,$(BUILD_TYPE)),) # NON-SYSTEM_GPGME

define gb_ExternalProject__use_gpgmepp
$(call gb_ExternalProject_use_external_project,$(1),gpgmepp)