graphics/librsvg2-rust: fix build on GCC architectures

Use newer GCC to link:
libtool: link: cc -I/usr/local/include/glib-2.0 -I/usr/local/lib/glib-2.0/include -I/usr/local/include -I/usr/local/include/gio-unix-2.0/ -I/usr/local/include/gdk-pixbuf-2.0 -I/usr/local/include/cairo -I/usr/local/include/pixman-1 -I/usr/local/include/freetype2 -I/usr/local/include/libdrm -I/usr/local/include/libpng16 -I/usr/local/include/pango-1.0 -I/usr/local/include/fribidi -D_THREAD_SAFE -pthread -I/usr/local/include/harfbuzz -O2 -pipe -fstack-protector-strong -fno-strict-aliasing -fstack-protector-strong -o .libs/rsvg-convert rsvg_convert-rsvg-convert.o ./.libs/librsvg-2.so -L/usr/local/lib -lpng16 -lz -lcairo-gobject -lgdk_pixbuf-2.0 -lgio-2.0 -lharfbuzz -lxml2 -lpangocairo-1.0 -lcairo -lpthread -lpangoft2-1.0 -lpango-1.0 -lgobject-2.0 -lglib-2.0 -lintl -lfontconfig -lfreetype -lm -pthread -Wl,-rpath -Wl,/usr/local/lib
./.libs/librsvg-2.so: undefined reference to `.TOC.'