Working on repl, not fully working yet, read more

After a few hours struggling with the linker, I've got the main.c file
running correctly, with caveats:

- must be executed from out/
- only building on linux for the moment
- no tests written yet

I will write some CI jobs to see if the repl works eventually.

repl/makefile

@@ -0,0 +1,76 @@
+#compiler settings
+CC=gcc
+CFLAGS+=-g -Wall -Werror -Wno-unused-parameter -Wno-unused-function -Wno-unused-variable
+LIBS+=-lm -lToy
+LDFLAGS+=-Wl,-rpath,'.'
+
+#directories
+REPL_ROOTDIR=..
+REPL_REPLDIR=.
+REPL_SOURCEDIR=$(REPL_ROOTDIR)/source
+
+REPL_OUTDIR=$(REPL_ROOTDIR)/out
+REPL_OBJDIR=obj
+
+#file names
+REPL_REPLFILES=$(wildcard $(REPL_REPLDIR)/*.c)
+REPL_OBJFILES=$(addprefix $(REPL_OBJDIR)/,$(notdir $(REPL_REPLFILES:.c=.o)))
+REPL_TARGETNAME=repl.exe
+
+#linker fix
+LDFLAGS+=-L$(realpath $(shell pwd)/$(REPL_OUTDIR))
+
+#build the object files, compile the test cases, and run
+all: clean build link
+
+#targets for each step
+.PHONY: build
+build: $(REPL_OBJDIR) $(REPL_OBJFILES)
+
+.PHONY: link
+link: $(REPL_OUTDIR) $(REPL_OUTDIR)/$(REPL_TARGETNAME)
+
+#util targets
+$(REPL_OUTDIR):
+	mkdir $(REPL_OUTDIR)
+
+$(REPL_OBJDIR):
+	mkdir $(REPL_OBJDIR)
+
+#compilation steps
+$(REPL_OBJDIR)/%.o: $(REPL_REPLDIR)/%.c
+	$(CC) -c -o $@ $< $(addprefix -I,$(REPL_REPLDIR)) $(addprefix -I,$(REPL_SOURCEDIR)) $(CFLAGS)
+
+$(REPL_OUTDIR)/$(REPL_TARGETNAME): $(REPL_OBJFILES)
+	$(CC) -DTOY_IMPORT $(CFLAGS) -o $@ $(REPL_OBJFILES) $(LDFLAGS) $(LIBS)
+
+#util commands
+.PHONY: clean
+clean:
+ifeq ($(shell uname),Linux)
+	find . -type f -name '*.o' -delete
+	find . -type f -name '*.a' -delete
+	find . -type f -name '*.exe' -delete
+	find . -type f -name '*.dll' -delete
+	find . -type f -name '*.lib' -delete
+	find . -type f -name '*.so' -delete
+	find . -type f -name '*.dylib' -delete
+	find . -type d -name 'out' -delete
+	find . -type d -name 'obj' -delete
+else ifeq ($(OS),Windows_NT)
+	$(RM) *.o *.a *.exe *.dll *.lib *.so *.dylib
+	$(RM) out
+	$(RM) obj
+else ifeq ($(shell uname),Darwin)
+	find . -type f -name '*.o' -delete
+	find . -type f -name '*.a' -delete
+	find . -type f -name '*.exe' -delete
+	find . -type f -name '*.dll' -delete
+	find . -type f -name '*.lib' -delete
+	find . -type f -name '*.so' -delete
+	find . -type f -name '*.dylib' -delete
+	find . -type d -name 'out' -delete
+	find . -type d -name 'obj' -delete
+else
+	@echo "Deletion failed - what platform is this?"
+endif