Add support for building macOS dylibs.

Build whiptcl and python modules as bundles, not dylibs.

TODO: PR URLs
--- Makefile.in.orig	2025-03-10 08:29:06.000000000 -0500
+++ Makefile.in	2025-08-14 10:26:57.000000000 -0500
@@ -7,16 +7,22 @@
 LDFLAGS = @LDFLAGS@
 CPPFLAGS = -D_GNU_SOURCE @CPPFLAGS@
 GNU_LD = @GNU_LD@
+UNAME_S := $(shell uname -s)
 
 VERSION = @VERSION@
 TAG = r$(subst .,-,$(VERSION))
 SONAME = @SONAME@
+ifeq ($(UNAME_S),Darwin)
+SOEXT = dylib
+else
 SOEXT = so
+endif
+BUNDLEEXT = so
 
 PYTHONVERS = @PYTHONVERS@
 WHIPTCLLIB = @WHIPTCLLIB@
 ifneq ($(WHIPTCLLIB),)
-WHIPTCLSO = $(WHIPTCLLIB).$(SOEXT)
+WHIPTCLSO = $(WHIPTCLLIB).$(BUNDLEEXT)
 else
 WHIPTCLSO =
 endif
@@ -26,17 +32,30 @@
 NDIALOGOBJS = whiptail.o dialogboxes.o
 WHIPTCLOBJS = shared/whiptcl.o shared/dialogboxes.o
 LIBNEWT = libnewt.a
+ifeq ($(UNAME_S),Darwin)
+SHARED = -dynamiclib
+BUNDLE = -bundle
+LIBNEWTSH = libnewt.$(VERSION).$(SOEXT)
+LIBNEWTSONAME = libnewt.$(SONAME).$(SOEXT)
+else
+SHARED = -shared
+BUNDLE = -shared
 LIBNEWTSH = libnewt.$(SOEXT).$(VERSION)
 LIBNEWTSONAME = libnewt.$(SOEXT).$(SONAME)
+endif
 LIBOBJS = newt.o button.o form.o checkbox.o entry.o label.o listbox.o \
           scrollbar.o textbox.o scale.o grid.o windows.o buttonbar.o \
 	  checkboxtree.o
 
+ifeq ($(UNAME_S),Darwin)
+SHLIBFLAGS= -install_name $(libdir)/$(LIBNEWTSONAME) -current_version $(VERSION) -compatibility_version $(SONAME)
+else
 ifneq ($(GNU_LD),)
 SHLIBFLAGS= -Wl,--version-script,newt.0.52.ver -Wl,-soname,$(LIBNEWTSONAME)
 else
 SHLIBFLAGS=
 endif
+endif
 
 SHCFLAGS = -fPIC
 
@@ -65,7 +84,7 @@
 TARGET=depend $(PROGS)
 endif
 
-all:	$(TARGET) _snack.$(SOEXT)
+all:	$(TARGET) _snack.$(BUNDLEEXT)
 
 test:	test.o $(LIBNEWT)
 	$(CC) -g -o test test.o $(LIBNEWT) $(LDFLAGS) $(LIBS)
@@ -82,7 +101,7 @@
 showkey:	showkey.o $(LIBNEWT)
 	$(CC) -g -o showkey showkey.o $(LIBNEWT) $(LDFLAGS) $(LIBS)
 
-_snack.$(SOEXT):   snack.c $(LIBNEWTSH)
+_snack.$(BUNDLEEXT):	snack.c $(LIBNEWTSH)
 ifneq ($(PYTHONVERS),)
 	@for ver in $(PYTHONVERS); do \
 		pyconfig=$$ver-config; \
@@ -96,8 +115,8 @@
 		PLDFLAGS=`$$pyconfig --ldflags --embed || $$pyconfig --ldflags`; \
 		echo $(CC) $(SHCFLAGS) $(CFLAGS) $(CPPFLAGS) $$PCFLAGS -c -o $$ver/snack.o snack.c; \
 		$(CC) $(SHCFLAGS) $(CFLAGS) $(CPPFLAGS) $$PCFLAGS -c -o $$ver/snack.o snack.c; \
-		echo $(CC) --shared $(LDFLAGS) $$PLDFLAGS -o $$ver/_snack.$(SOEXT) $$ver/snack.o -L. -lnewt $(LIBS); \
-		$(CC) --shared $(LDFLAGS) $$PLDFLAGS -o $$ver/_snack.$(SOEXT) $$ver/snack.o -L. -lnewt $(LIBS); \
+		echo $(CC) $(BUNDLE) $(LDFLAGS) $$PLDFLAGS -o $$ver/_snack.$(BUNDLEEXT) $$ver/snack.o -L. -lnewt $(LIBS); \
+		$(CC) $(BUNDLE) $(LDFLAGS) $$PLDFLAGS -o $$ver/_snack.$(BUNDLEEXT) $$ver/snack.o -L. -lnewt $(LIBS); \
 	done
 endif
 	touch $@
@@ -105,8 +124,8 @@
 whiptail: $(NDIALOGOBJS) $(LIBNEWTSH)
 	$(CC) -g -o whiptail $(NDIALOGOBJS) -L. $(LDFLAGS) -lnewt $(LIBS) -lpopt
 
-whiptcl.$(SOEXT): $(WHIPTCLOBJS) $(LIBNEWTSH)
-	$(CC) -shared $(SHCFLAGS) $(LDFLAGS) -o whiptcl.$(SOEXT) $(WHIPTCLOBJS) -L. -lnewt  $(LIBTCL) -lpopt $(LIBS)
+$(WHIPTCLSO): $(WHIPTCLOBJS) $(LIBNEWTSH)
+	$(CC) $(BUNDLE) $(SHCFLAGS) $(LDFLAGS) -o $(WHIPTCLSO) $(WHIPTCLOBJS) -L. -lnewt $(LIBTCL) -lpopt $(LIBS)
 
 $(LIBNEWT): $(LIBOBJS)
 	ar rv $@ $^
@@ -118,7 +137,7 @@
 
 clean:
 	rm -f $(PROGS) *.o $(LIBNEWT) core $(LIBNEWTSH)  \
-		$(SHAREDDIR)/*.o *.$(SOEXT)*
+		$(SHAREDDIR)/*.o *.$(SOEXT)* *.$(BUNDLEEXT)
 
 depend:
 	$(CC) $(CFLAGS) $(CPPFLAGS) -M $(SOURCES) > .depend
@@ -126,7 +145,7 @@
 sharedlib: $(LIBNEWTSH)
 
 $(LIBNEWTSH): $(SHAREDOBJS)
-	$(CC) -shared -o $(LIBNEWTSH) $(SHLIBFLAGS) $(SHAREDOBJS) $(LDFLAGS) $(LIBS)
+	$(CC) $(SHARED) -o $(LIBNEWTSH) $(SHLIBFLAGS) $(SHAREDOBJS) $(LDFLAGS) $(LIBS)
 	ln -fs $(LIBNEWTSONAME) libnewt.$(SOEXT)
 	ln -fs $(LIBNEWTSH) $(LIBNEWTSONAME)
 
@@ -159,13 +178,13 @@
 	install -m 755 $(WHIPTCLSO) $(instroot)/$(libdir)
 endif
 
-install-py: _snack.$(SOEXT)
+install-py: _snack.$(BUNDLEEXT)
 ifneq ($(PYTHONVERS),)
 	@for ver in $(PYTHONVERS); do \
 		PLATLIB=`$$ver -c "import sysconfig; print(sysconfig.get_path('platlib'))"`; \
 		[ -d $(instroot)/$$PLATLIB ] || install -m 755 -d $(instroot)/$$PLATLIB ;\
-		echo install -m 755 $$ver/_snack.$(SOEXT) $(instroot)/$$PLATLIB;\
-		install -m 755 $$ver/_snack.$(SOEXT) $(instroot)/$$PLATLIB;\
+		echo install -m 755 $$ver/_snack.$(BUNDLEEXT) $(instroot)/$$PLATLIB;\
+		install -m 755 $$ver/_snack.$(BUNDLEEXT) $(instroot)/$$PLATLIB;\
 		echo install -m 644 snack.py $(instroot)/$$PLATLIB;\
 		install -m 644 snack.py $(instroot)/$$PLATLIB;\
 	done