We accidentally set SUBPACKAGES to an empty string, which breaks the "run" target in the root Makefile

- Use PROVIDERS in place of SUBPACKAGES if set
- Use REPO in place of XPKG_REG_ORGS if set

Signed-off-by: Alper Rifat Ulucinar <ulucinar@users.noreply.github.com>

Author: ulucinar

Makefile

@@ -324,10 +324,11 @@ DEP_CONSTRAINT ?= >= 0.0.0
 ifeq (-,$(findstring -,$(VERSION)))
     DEP_CONSTRAINT = >= 0.0.0-0
 endif
-# Define SUBPACKAGES variable and set its value from PROVIDERS
-SUBPACKAGES := $(PROVIDERS)
-# Define XPKG_REG_ORGS variable and set its value from REPO
-XPKG_REG_ORGS := $(REPO)
+
+# use PROVIDERS in place of SUBPACKAGES if set
+SUBPACKAGES := $(if $(PROVIDERS),$(PROVIDERS),$(SUBPACKAGES))
+# use REPO in place of XPKG_REG_ORGS if set
+XPKG_REG_ORGS := $(if $(REPO),$(REPO),$(XPKG_REG_ORGS))
 load-pkg: $(UP) build.all
 	@$(INFO) Loading the family providers into the Docker daemon: $(SUBPACKAGES)
 	@for p in $(PLATFORMS); do \