qt5-base: create symlink '$PREFIX/lib/fonts' --> '/system/fonts' if possible

Quick fix for applications that require fonts.

x11-packages/qt5-base/build.sh

@@ -219,3 +219,9 @@ termux_step_make_install() {
     find "${TERMUX_PREFIX}/lib" -type f -name '*.prl' \
         -exec sed -i -e '/^QMAKE_PRL_BUILD_DIR/d' "{}" \;
 }
+
+termux_step_create_debscripts() {
+    ## FIXME: Qt should be built with fontconfig somehow instead
+    ## of using direct path to fonts.
+    cp -f "${TERMUX_PKG_BUILDER_DIR}/postinst" ./
+}

x11-packages/qt5-base/postinst

@@ -0,0 +1,7 @@
+#!/data/data/com.termux/files/usr/bin/sh
+
+if [ ! -e "/data/data/com.termux/files/usr/lib/fonts" ]; then
+    if [ -d "/system/fonts" ]; then
+        ln -sf /system/fonts /data/data/com.termux/files/usr/lib/fonts
+    fi
+fi