xbps-src: install cross pkg after checking dependencies.

... this should help buildbot a bit more.

common/xbps-src/libexec/build.sh

@@ -43,6 +43,10 @@ if [ "$PKGNAME" != "$XBPS_TARGET_PKG" -o -z "$XBPS_SKIP_DEPS" ]; then
     install_pkg_deps $PKGNAME $XBPS_TARGET_PKG pkg $XBPS_CROSS_BUILD $XBPS_CROSS_PREPARE || exit $?
 fi
 
+if [ "$XBPS_CROSS_BUILD" ]; then
+    install_cross_pkg $XBPS_CROSS_BUILD || exit $?
+fi
+
 # Fetch distfiles after installing required dependencies,
 # because some of them might be required for do_fetch().
 $XBPS_LIBEXECDIR/xbps-src-dofetch.sh $SOURCEPKG $XBPS_CROSS_BUILD || exit 1

common/xbps-src/shutils/cross.sh

@@ -54,8 +54,6 @@ prepare_cross_sysroot() {
     ln -s usr/include ${XBPS_CROSS_BASE}/include
     ln -s usr/lib ${XBPS_CROSS_BASE}/lib
 
-    install_cross_pkg $cross || return 1
-
     touch -f $statefile
 
     return 0