--- lib/libpng/scripts/makefile.std.orig	2010-12-09 16:48:13.000000000 +0300
+++ lib/libpng/scripts/makefile.std	2011-04-13 20:38:46.000000000 +0400
@@ -27,12 +27,16 @@
 ZLIBLIB=../zlib
 ZLIBINC=../zlib
 
-CC=cc
-AR_RC=ar rc
-MKDIR_P=mkdir
-LN_SF=ln -sf
-RANLIB=ranlib
-RM_F=rm -f
+CC?=cc
+AR?=ar
+AR_RC=${AR} rc
+MKDIR?=mkdir
+MKDIR_P=${MKDIR}
+LN?=ln
+LN_SF=${LN} -sf
+RANLIB?=ranlib
+RM?=rm
+RM_F=${RM} -f
 
 CFLAGS=-I$(ZLIBINC) -O # -g -DPNG_DEBUG=5
 LDFLAGS=-L. -L$(ZLIBLIB) -lpng -lz -lm