[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/trunk/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
+USE_LIBDL := 1
 
 include $(LEVEL)/Makefile.rules
 
 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
 

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

 LEVEL := ../../make
 
 CXX_SOURCES := main.cpp
-LD_EXTRAS := -ldl
+USE_LIBDL := 1
 
 include $(LEVEL)/Makefile.rules
 
 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

lldb/trunk/packages/Python/lldbsuite/test/make/Makefile.rules

else ifeq "$(OS)" "Android"
     # Android.rules.
   else
     CXXFLAGS += -stdlib=libc++
     LDFLAGS += -stdlib=libc++
   endif
 endif
 
 #----------------------------------------------------------------------
+# Additional system libraries
+#----------------------------------------------------------------------
+ifeq (1,$(USE_LIBDL))
+  ifneq ($(OS),NetBSD)
+    LDFLAGS += -ldl
+  endif
+endif
+
+#----------------------------------------------------------------------
 # dylib settings
 #----------------------------------------------------------------------
 ifneq "$(strip $(DYLIB_C_SOURCES))" ""
   DYLIB_OBJECTS +=$(strip $(DYLIB_C_SOURCES:.c=.o))
 endif
 
 ifneq "$(strip $(DYLIB_OBJC_SOURCES))" ""
   DYLIB_OBJECTS +=$(strip $(DYLIB_OBJC_SOURCES:.m=.o))