packages: setup_toolchain $TARGET only called after package is sourced

Packages referencing variables defined in setup_toolchain such as CC, CXX,
AR, CFLAGS, LDFLAGS, HOST_CC etc. etc. must only reference these variables in
pre_build()/pre_configure()/pre_make() etc. functions, as the variables will not
be available when the package is sourced, but will be available after the call
to setup_toolchain() from scripts/build.

packages/graphics/vsxu/package.mk

@@ -1,5 +1,6 @@
 # SPDX-License-Identifier: GPL-2.0-or-later
 # Copyright (C) 2009-2016 Stephan Raue (stephan@openelec.tv)
+# Copyright (C) 2018-present Team LibreELEC (https://libreelec.tv)
 
 PKG_NAME="vsxu"
 PKG_VERSION="0.5.1"
@@ -12,13 +13,15 @@ PKG_URL="$DISTRO_SRC/$PKG_NAME-$PKG_VERSION.tar.gz"
 PKG_DEPENDS_TARGET="toolchain $OPENGL libX11 glew glfw zlib libpng libjpeg-turbo freetype"
 PKG_LONGDESC="an OpenGL-based programming environment to visualize music and create graphic effects"
 
-export LDFLAGS="$LDFLAGS -lX11"
-
 PKG_CMAKE_OPTS_TARGET="-DBUILD_SHARED_LIBS=0 \
                        -DVSXU_STATIC=1 \
                        -DCMAKE_POSITION_INDEPENDENT_CODE=1 \
                        -DCMAKE_CXX_FLAGS=-I$SYSROOT_PREFIX/usr/include/freetype2"
 
+pre_configure_target(){
+  export LDFLAGS="$LDFLAGS -lX11"
+}
+
 post_makeinstall_target() {
   mkdir -p $SYSROOT_PREFIX/usr/lib/vsxu
   cp -PR $INSTALL/usr/lib/* $SYSROOT_PREFIX/usr/lib