Added --print-target-path option.

If cc65 is installed and used as designed there's no need whatsoever for CC65_HOME (both on *IX and Windows) from the perspective of the cc65 binaries. If the user however has to access files from the 'target' directory thenhe ends up with some assumption on the cc65 installation path nevertheless :-(

In order to avoid this I added the --print-target-path option. It "exports" the logic used by the cc65 binaries to locate their files to the user thus allowing him to leverage the same logic to locate the target files in his build scripts / Makefiles.

src/Makefile

@@ -24,6 +24,7 @@ datadir := $(if $(prefix),$(prefix)/share/cc65,$(abspath ..))
 
 CA65_INC = $(datadir)/asminc
 CC65_INC = $(datadir)/include
+CL65_TGT = $(datadir)/target
 LD65_LIB = $(datadir)/lib
 LD65_OBJ = $(datadir)/lib
 LD65_CFG = $(datadir)/cfg
@@ -63,8 +64,9 @@ endif
 
 CFLAGS += -MMD -MP -O -I common \
           -Wall -Wextra -Wno-char-subscripts $(USER_CFLAGS) \
-          -DGIT_SHA=$(GIT_SHA) -DCA65_INC=$(CA65_INC) -DCC65_INC=$(CC65_INC) \
+          -DCA65_INC=$(CA65_INC) -DCC65_INC=$(CC65_INC) -DCL65_TGT=$(CL65_TGT) \
           -DLD65_LIB=$(LD65_LIB) -DLD65_OBJ=$(LD65_OBJ) -DLD65_CFG=$(LD65_CFG)
+          -DGIT_SHA=$(GIT_SHA)
 
 LDLIBS += -lm