qemu-kvm: fixed to only inject library path for libx11 if it is really installed

emulators/qemu-kvm/qemu-kvm.conf

@@ -2,7 +2,7 @@
 # This copyright note is auto-generated by ./scripts/Create-CopyPatch.
 #
 # Filename: package/.../qemu-kvm/qemu-kvm.conf
-# Copyright (C) 2010 - 2011 The OpenSDE Project
+# Copyright (C) 2010 - 2013 The OpenSDE Project
 #
 # More information can be found in the files COPYING and README.
 #
@@ -16,4 +16,6 @@
 # installed at the right place and to avoid shared files with qemu
 datadir="$datadir/$pkg"
 
-var_append GCC_WRAPPER_INSERT ' ' "-L$(pkgprefix libdir libx11)"
+if pkginstalled -f libx11; then
+	var_append GCC_WRAPPER_INSERT ' ' "-L$(pkgprefix libdir libx11)"
+fi