Use system libraries

--- a/cc0/Makefile
+++ b/cc0/Makefile
@@ -22,12 +22,12 @@ MLTON_BASIC = mlton $(MLTON_FLAGS) -verbose $(MLTON_VERB)  -output
 MLTON_NATIVE := mlton -default-ann "redundantMatch error" -default-ann "sequenceNonUnit error"
 MLTON_NATIVE += -link-opt "-lpthread -ldl -rdynamic" -cc-opt "-Iinclude" -default-ann "allowFFI true"
 MLTON_NATIVE += -cc-opt "-I../externals/"
-MLTON_NATIVE += -link-opt "../externals/readline/libreadline.a ../externals/readline/libhistory.a"
+MLTON_NATIVE += -link-opt "$(shell pkg-config readline --libs)"
 MLTON_NATIVE += -link-opt "$(shell pkg-config libpng --libs)"
 
 # libreadline dependencies
 ifeq ($(PLATFORM),osx)
-MLTON_NATIVE += -link-opt "-ltermcap"
+MLTON_NATIVE += -link-opt "-lncurses"
 else
 # (Assuming Linux)
 MLTON_NATIVE += -link-opt "-ltinfo"
@@ -122,9 +122,9 @@ endef
 
 $(foreach rt,$(RUNTIMES),$(eval $(call runtime_template,$(rt))))
 
-c0rt/$(call dllname,c0rt): gc libbacktrace
+c0rt/$(call dllname,c0rt):
 
-unsafe/$(call dllname,unsafe): gc
+unsafe/$(call dllname,unsafe):
 
 
 ### cc0 - the C0 compiler
@@ -222,7 +222,6 @@ NATIVE_COIN    = $(NATIVE_CYMBOL) $(NATIVE_CALLING)
 NATIVE_COIN += coin/c0readline.c
 
 COIN_DEPS = $(CC0_DEPS) $(NATIVE_COIN) cymbol/cymbol*.cm cymbol/*.sml cymbol/*.mlb coin/coin*.cm coin/*.sml coin/*.sml
-COIN_DEPS += readline
 
 .PHONY: coin
 coin: bin/coin
--- a/cc0/lib.mk
+++ b/cc0/lib.mk
@@ -15,9 +15,9 @@ TARGET = $(call dllname,$(LIBNAME))
 endif
 
 # These libs are handled specially by this file
-NATIVELIBS = gc ncurses backtrace
+NATIVELIBS =
 C0LIBS = $(filter-out $(NATIVELIBS),$(REQUIRES))
-LIBS = -L$(abspath $(DEPTH)/lib) $(patsubst %,$(DEPTH)/lib/$(call dllname,%),$(C0LIBS))
+LIBS = -L$(abspath $(DEPTH)/lib)
 LDFLAGS = 
 
 # -fPIC is not supported on Windows and is not necessary there because we link statically