Bug 1172668 - Unbreak DMD on OS X after bug 1168719. r=gps

Bug 1168719 added a generic replace malloc library which name happened to be
the same as the existing dummy library used to link replace malloc on OSX.
Change the name of that dummy library.

memory/replace/dummy/moz.build

@@ -9,6 +9,6 @@ SOURCES += [
     'dummy_replace_malloc.c',
 ]
 
-SharedLibrary('replace_malloc')
+SharedLibrary('dummy_replace_malloc')
 
 DISABLE_STL_WRAPPING = True

mozglue/build/replace_malloc.mk

@@ -25,6 +25,8 @@ ifneq ($(MOZ_REPLACE_MALLOC_LINKAGE),compiler support)
 OS_LDFLAGS += -flat_namespace
 endif
 ifeq ($(MOZ_REPLACE_MALLOC_LINKAGE),dummy library)
-OS_LDFLAGS += -Wl,-weak_library,$(DEPTH)/memory/replace/dummy/$(DLL_PREFIX)replace_malloc$(DLL_SUFFIX)
+OS_LDFLAGS += -Wl,-weak_library,$(DEPTH)/memory/replace/dummy/$(DLL_PREFIX)dummy_replace_malloc$(DLL_SUFFIX)
 endif
+
+EXTRA_DEPS += $(topsrcdir)/mozglue/build/replace_malloc.mk
 endif