automake: fix some occurrences of hardcoded -ldl and -lpthread

Correct some occurrences of -ldl and -lpthread to use
$(DLOPEN_LIBS) and $(PTHREAD_LIBS) respectively.

Signed-off-by: Jonathan Gray <jsg@jsg.id.au>
Cc: "11.0 11.1" <mesa-stable@lists.freedesktop.org>
Reviewed-by: Emil Velikov <emil.l.velikov@gmail.com>

src/gallium/targets/opencl/Makefile.am

@@ -20,7 +20,7 @@ lib@OPENCL_LIBNAME@_la_LIBADD = \
 	$(top_builddir)/src/gallium/auxiliary/libgallium.la \
 	$(top_builddir)/src/util/libmesautil.la \
 	$(ELF_LIB) \
-	-ldl \
+	$(DLOPEN_LIBS) \
 	-lclangCodeGen \
 	-lclangFrontendTool \
 	-lclangFrontend \

src/mesa/drivers/dri/i965/Makefile.am

@@ -51,7 +51,8 @@ libi965_compiler_la_SOURCES = $(i965_compiler_FILES)
 TEST_LIBS = \
 	libi965_compiler.la \
         ../../../libmesa.la \
-	-lpthread -ldl \
+	$(PTHREAD_LIBS) \
+	$(DLOPEN_LIBS) \
 	../common/libdri_test_stubs.la
 
 TESTS = \