[osx] Ease compiling on Snow Leopard

Now compiling on Snow Leopard should be as simple as, for example:
CC=clang++-mp-9.0 CPP=clang++-mp-9.0 OBJCC=clang++-mp-9.0 CPPFLAGS=-stdlib=libc++ OBJCFLAGS=-stdlib=libc++ make

pc/Makefile

@@ -23,9 +23,9 @@ SHARED_DIR = shared/
 PROJ_DIR = ext
 #
 
-CC=$(CROSS_COMPILE)g++
-CPP=$(CROSS_COMPILE)g++
-OBJCC=$(CROSS_COMPILE)g++
+CC ?= $(CROSS_COMPILE)g++
+CPP ?= $(CROSS_COMPILE)g++
+OBJCC ?= $(CROSS_COMPILE)g++
 debug = -g
 optimize = -O3
 
@@ -259,12 +259,12 @@ $(BIN)/$(DEC7Z): $(PROJ_DIR)/lzma1505/C/Util/7z/$(DEC7Z) $(PROJ_DIR)/lzma1505/C/
 	cp $(PROJ_DIR)/lzma1505/C/Util/7z/$(DEC7Z) $(BIN)
 
 $(PROJ_DIR)/lzma1505/C/Util/7z/$(DEC7Z):
-	uname_S=$(uname_S) make -C $(PROJ_DIR)/lzma1505/C/Util/7z -f makefile.gcc
+	uname_S=$(uname_S) LDFLAGS= CFLAGS= make -C $(PROJ_DIR)/lzma1505/C/Util/7z -f makefile.gcc
 
 $(BIN)/$(UNRAR): $(PROJ_DIR)/unrar/$(UNRAR)
 	cp $(PROJ_DIR)/unrar/$(UNRAR) $(BIN)
 $(PROJ_DIR)/unrar/$(UNRAR):
-	uname_S=$(uname_S) make -C $(PROJ_DIR)/unrar
+	uname_S=$(uname_S) CPPFLAGS= LDFLAGS= make -C $(PROJ_DIR)/unrar
 
 $(LIBJDKMIDI_LIB): $(LIBJDKMIDI_OSDIR)/Makefile
 	cd $(LIBJDKMIDI_OSDIR) && make

pc/ext/lzma1505/C/Util/7z/makefile.gcc

@@ -8,8 +8,10 @@ else ifeq ($(uname_S), Cross_Windows)
 endif
 
 ifeq ($(uname_S), Darwin)
-	OSX_BACKSUPPORT = -arch x86_64 -mmacosx-version-min=10.9 \
-	-DMAC_OS_X_VERSION_MIN_REQUIRED=1090
+	ifeq ($(OSX_BACKSUPPORT), 1)
+		OSX_BACKSUPPORT = -arch x86_64 -mmacosx-version-min=10.9 \
+		-DMAC_OS_X_VERSION_MIN_REQUIRED=1090
+	endif
 	CFLAGS += $(OSX_BACKSUPPORT)
 	LDFLAGS += $(OSX_BACKSUPPORT)
 endif

pc/ext/unrar/makefile

@@ -12,8 +12,10 @@ else ifeq ($(uname_S), Cross_Windows)
 endif
 
 ifeq ($(uname_S), Darwin)
-	OSX_BACKSUPPORT = -arch x86_64 -mmacosx-version-min=10.9 \
-	-DMAC_OS_X_VERSION_MIN_REQUIRED=1090
+	ifeq ($(OSX_BACKSUPPORT), 1)
+		OSX_BACKSUPPORT = -arch x86_64 -mmacosx-version-min=10.9 \
+		-DMAC_OS_X_VERSION_MIN_REQUIRED=1090
+	endif
 	CXXFLAGS += $(OSX_BACKSUPPORT)
 	LDFLAGS += $(OSX_BACKSUPPORT)
 endif