Fix removal of GPL libs (#60100)

`$(build_datarootdir)/lib/julia` doesn't exist, libraries are in
`$(build_private_libdir)`.

See https://github.com/JuliaLang/julia/pull/59627/files#r2510807584.

Author: nalimilan

stdlib/Makefile

@@ -15,7 +15,6 @@ include $(JULIAHOME)/deps/*.version
 
 VERSDIR := v$(shell cut -d. -f1-2 < $(JULIAHOME)/VERSION)
 DIRS := $(build_datarootdir)/julia/stdlib/$(VERSDIR) $(build_prefix)/manifest/$(VERSDIR)
-LIBDIR := $(build_datarootdir)/lib/julia
 
 $(foreach dir,$(DIRS),$(eval $(call dir_target,$(dir))))
 
@@ -65,11 +64,11 @@ STDLIBS_LINK_TARGETS := $(addprefix $(build_datarootdir)/julia/stdlib/$(VERSDIR)
 remove-gpl-libs:
 ifeq ($(USE_GPL_LIBS),0)
 	@echo Removing GPL libs...
-	-rm -f $(LIBDIR)/libcholmod*
-	-rm -f $(LIBDIR)/libklu_cholmod*
-	-rm -f $(LIBDIR)/librbio*
-	-rm -f $(LIBDIR)/libspqr*
-	-rm -f $(LIBDIR)/libumfpack*
+	-rm -f $(build_private_libdir)/libcholmod*
+	-rm -f $(build_private_libdir)/libklu_cholmod*
+	-rm -f $(build_private_libdir)/librbio*
+	-rm -f $(build_private_libdir)/libspqr*
+	-rm -f $(build_private_libdir)/libumfpack*
 endif
 
 getall get: $(addprefix get-, $(STDLIBS_EXT) $(JLL_NAMES))