os/2 optionally builds against libiconv.

Makefile.os2

@@ -1,10 +1,16 @@
 # Open Watcom makefile to build SDL2.dll for OS/2
 # wmake -f Makefile.os2
+#
+# If you have libiconv installed, you can compile against it
+# by specifying LIBICONV=1, e.g.:
+# wmake -f Makefile.os2 LIBICONV=1
 
 LIBNAME = SDL2
 VERSION = 2.0.19
 DESCRIPTION = Simple DirectMedia Layer 2
 
+LIBICONV=0
+
 LIBHOME = .
 DLLFILE = $(LIBHOME)/$(LIBNAME).dll
 LIBFILE = $(LIBHOME)/$(LIBNAME).lib
@@ -23,7 +29,12 @@ CFLAGS+= -wcd=303
 # building dll:
 CFLAGS+= -bd
 # iconv:
+!ifeq LIBICONV 1
+CFLAGS+= -DHAVE_ICONV=1 -DHAVE_ICONV_H=1
+LIBS+= iconv.lib
+!else
 LIBS+= libuls.lib libconv.lib
+!endif
 # the include paths :
 CFLAGS+= $(INCPATH)
 # building SDL itself (for DECLSPEC):
@@ -69,7 +80,9 @@ SRCS+= SDL_locale.c SDL_syslocale.c
 SRCS+= SDL_url.c SDL_sysurl.c
 
 SRCS+= SDL_os2.c
+!ifeq LIBICONV 0
 SRCS+= geniconv.c os2cp.c os2iconv.c sys2utf8.c
+!endif
 SRCS+= SDL_os2audio.c
 SRCS+= SDL_os2video.c SDL_os2util.c SDL_os2dive.c SDL_os2vman.c &
        SDL_os2mouse.c SDL_os2messagebox.c