packages sdl_image vigra: use pkg-config for png and tiff

src/sdl_image.mk

@@ -20,8 +20,7 @@ define $(PKG)_UPDATE
 endef
 
 define $(PKG)_BUILD
-    $(SED) -i 's,^\(Requires:.*\),\1 libpng,' '$(1)/SDL_image.pc.in'
-    echo 'Libs.private: -ltiff -ljpeg -lz' >> '$(1)/SDL_image.pc.in'
+    $(SED) -i 's,^\(Requires:.*\),\1 libtiff-4 libpng,' '$(1)/SDL_image.pc.in'
     cd '$(1)' && ./configure \
         --host='$(TARGET)' \
         --disable-shared \

src/vigra.mk

@@ -39,5 +39,5 @@ define $(PKG)_BUILD
     $(TARGET)-g++ \
         '$(2).cpp' -o $(PREFIX)/$(TARGET)/bin/test-vigra.exe \
         -DVIGRA_STATIC_LIB \
-        -lvigraimpex `'$(TARGET)-pkg-config' OpenEXR --cflags --libs` -ltiff -lpng -ljpeg -lz
+        -lvigraimpex `'$(TARGET)-pkg-config' OpenEXR libtiff-4 libpng --cflags --libs` -ljpeg
 endef