add Mac OS X support

use dylib shared lib extention
allow to specifiy os specific shared lib link option
Mac OS use -dynamiclib instead of -shared, -install_name instead of -soname
and does not support --version-script

add HOSTOS macro to detect the current os you are

Signed-off-by: Jean-Christophe PLAGNIOL-VILLARD <plagnioj@jcrosoft.com>

Makefile

@@ -28,6 +28,17 @@ BINDIR = $(PREFIX)/bin
 LIBDIR = $(PREFIX)/lib
 INCLUDEDIR = $(PREFIX)/include
 
+HOSTOS := $(shell uname -s | tr '[:upper:]' '[:lower:]' | \
+	    sed -e 's/\(cygwin\).*/cygwin/')
+
+ifeq ($(HOSTOS),darwin)
+SHAREDLIB_EXT=dylib
+SHAREDLIB_LINK_OPTIONS=-dynamiclib -Wl,-install_name -Wl,
+else
+SHAREDLIB_EXT=so
+SHAREDLIB_LINK_OPTIONS=-shared -Wl,--version-script=$(LIBFDT_version) -Wl,-soname,
+endif
+
 #
 # Overall rules
 #
@@ -116,7 +127,7 @@ endif
 LIBFDT_objdir = libfdt
 LIBFDT_srcdir = libfdt
 LIBFDT_archive = $(LIBFDT_objdir)/libfdt.a
-LIBFDT_lib = $(LIBFDT_objdir)/libfdt.so
+LIBFDT_lib = $(LIBFDT_objdir)/libfdt.$(SHAREDLIB_EXT)
 LIBFDT_include = $(addprefix $(LIBFDT_srcdir)/,$(LIBFDT_INCLUDES))
 LIBFDT_version = $(addprefix $(LIBFDT_srcdir)/,$(LIBFDT_VERSION))
 
@@ -220,8 +231,8 @@ clean: libfdt_clean tests_clean
 
 $(LIBFDT_lib):
 	@$(VECHO) LD $@
-	$(CC) $(LDFLAGS) -fPIC -Wl,--version-script=$(LIBFDT_version) -Wl,-soname,$(notdir $@) -shared -o $(LIBFDT_objdir)/libfdt-$(DTC_VERSION).so $^
-	ln -s libfdt-$(DTC_VERSION).so $(LIBFDT_objdir)/libfdt.so
+	$(CC) $(LDFLAGS) -fPIC $(SHAREDLIB_LINK_OPTIONS)$(notdir $@) -o $(LIBFDT_objdir)/libfdt-$(DTC_VERSION).$(SHAREDLIB_EXT) $^
+	ln -sf libfdt-$(DTC_VERSION).$(SHAREDLIB_EXT) $(LIBFDT_objdir)/libfdt.$(SHAREDLIB_EXT)
 
 %.lex.c: %.l
 	@$(VECHO) LEX $@