[lldb] [test] Do not link -ldl on NetBSD

[mgorny]

Summary

Fix the load_* using test Makefiles not to link -ldl on NetBSD.
There is no such a library on NetBSD, and dlopen() is available
without a library. Quoting the manpage:

(These functions are not in a library.  They are included in every
dynamically linked program automatically.)

To resolve this portably, introduce a new USE_LIBDL option. If it set
to 1, Makefile.rules automatically appends -ldl on platforms needing it.

[labath]

Could you define some variable like DL_LIBS in the main Makefile.rules? Then you could just do LD_EXTRAS := $(DL_LIBS) in the tests.

[mgorny]

Switched to appending -ldl via Makefile.rules, using USE_LIBDL option.

lldb/packages/Python/lldbsuite/test/functionalities/load_unload/Makefile

 LEVEL := ../../make
 
 LIB_PREFIX := loadunload_
 
-LD_EXTRAS := -L. -l$(LIB_PREFIX)d -ldl
+LD_EXTRAS := -L. -l$(LIB_PREFIX)d
 CXX_SOURCES := main.cpp
 
 include $(LEVEL)/Makefile.rules
 
+ifneq ($(OS),NetBSD)
+LD_EXTRAS += -ldl
+endif
+
 a.out: lib_a lib_b lib_c lib_d hidden_lib_d install_name_tool
 
 lib_%:
   $(MAKE) VPATH=$(SRCDIR) -I $(SRCDIR) -f $(SRCDIR)/$*.mk
 
 install_name_tool:
 ifeq ($(OS),Darwin)
   install_name_tool -id @executable_path/libloadunload_d.dylib libloadunload_d.dylib

lldb/packages/Python/lldbsuite/test/functionalities/load_using_paths/Makefile

 LEVEL := ../../make
 
 CXX_SOURCES := main.cpp
-LD_EXTRAS := -ldl
+LD_EXTRAS :=
 
 include $(LEVEL)/Makefile.rules
 
+ifneq ($(OS),NetBSD)
+LD_EXTRAS += -ldl
+endif
+
 all: hidden_lib a.out
 
 hidden_lib:
   $(MAKE) VPATH=$(SRCDIR)/hidden -I $(SRCDIR)/hidden -C hidden -f $(SRCDIR)/hidden/Makefile
 
 clean::
   $(MAKE) -I $(SRCDIR)/hidden -C hidden -f $(SRCDIR)/hidden/Makefile clean