[ft] Ignore libpng-config when cross-building

[suzuki toshiya]

Hi,

The current FreeType2 checks the PNG library availability
by libpng-config, if no options are given. It might cause
a wrong configuration under cross-building, because
libpng-config would return the info for the hosting system.

Some investigation is needed for better automation (e.g.
pkg-config? xxx-config with target name prefix? etc etc),
so I propose an insertion of a disabler of libpng-config
when cross-building, as a temporal fix. Any comments?
I want to hear the comments from the developers who established
their own cross building procedure for FreeType2.

Regards,
mpsuzuki



diff --git a/builds/unix/configure.raw b/builds/unix/configure.raw
index 6a6edc7..9798dbe 100644
--- a/builds/unix/configure.raw
+++ b/builds/unix/configure.raw
@@ -292,6 +292,10 @@ if test x$with_png != xno; then
       AC_MSG_ERROR([`libpng-config' not found;
 either set the LIBPNG_CFLAGS and LIBPNG_LDFLAGS environment variables,
 or pass `--without-png' to the `configure' script.])
+    elif test ${cross_compiling} = yes; then
+      AC_MSG_ERROR([`libpng-config' should not be used in cross-building,
+set the LIBPNG_CFLAGS and LIBPNG_LDFLAGS environment,
+or pass `--without-png' to the `configure' script.])
     fi
     LIBPNG_CFLAGS="`libpng-config --cflags`"
     LIBPNG_LDFLAGS="`libpng-config --ldflags`"