Remove Make.inc and simplify build

Makefile

@@ -9,7 +9,7 @@ clean:
 	rm -rf R-*
 
 R-$(RVERSION).tar.gz:
-	wget https://cran.r-project.org/src/base/R-4/$@
+	curl -L -O https://cran.r-project.org/src/base/R-4/$@
 
 update: R-$(RVERSION).tar.gz
 	tar -xzvf $< --strip-components 3 -C src --include '*/src/nmath/*.[ch]' \

src/Makefile

@@ -1,4 +1,28 @@
-include ../Make.inc
+# -*- mode: makefile -*-
+
+# Default value, can be overriden on the command line
+# or with an environment variable.
+CC ?= gcc
+
+OS = $(shell uname)
+
+ifneq (,$(findstring MINGW,$(OS)))
+override OS := Windows_NT
+endif
+ifneq (,$(findstring MSYS,$(OS)))
+override OS := Windows_NT
+endif
+ifneq (,$(findstring CYGWIN,$(OS)))
+override OS := Windows_NT
+endif
+
+ifeq ($(OS), Darwin)
+SHLIB_EXT = dylib
+else ifeq ($(OS), Windows_NT)
+SHLIB_EXT = dll
+else
+SHLIB_EXT = so
+endif
 
 SRCS  = $(wildcard *.c)
 OBJS  = $(SRCS:%.c=%.o)
@@ -10,21 +34,20 @@ else
 XOBJS = $(DOBJS)
 endif
 
-CFLAGS-add += -DMATHLIB_STANDALONE
-
+CFLAGS += -DMATHLIB_STANDALONE -fPIC -O3 -std=c99 -I../include
 
 default: release
 
 %.o: %.c
-	$(CC) $(CPPFLAGS) $(CFLAGS-add) $(CFLAGS) $(fPIC) -std=gnu99 -I../include -DNDEBUG -c $< -o $@
+	$(CC) $(CPPFLAGS) $(CFLAGS) -DNDEBUG -c $< -o $@
 %.do: %.c
-	$(CC) $(CPPFLAGS) $(CFLAGS-add) $(CFLAGS) $(fPIC) -std=gnu99 -I../include -g  -c $< -o $@
+	$(CC) $(CPPFLAGS) $(CFLAGS) -g  -c $< -o $@
 
 release debug: libRmath-julia.$(SHLIB_EXT)
 
 libRmath-julia.$(SHLIB_EXT): $(XOBJS)
 	-rm -f $@
-	$(CC) $(LDFLAGS-add) $(LDFLAGS) -shared -o $@ $^
+	$(CC) $(LDFLAGS) -shared -o $@ $^
 
 clean:
 	-rm -f *.o *.do *.a *.$(SHLIB_EXT) core* *~ *#