[libxslt] xslt-config.in: Fix broken --prefix=DIR support

[Nick Wellnhofer <nwellnhof src gnome org>]

commit 2477a0622aafff0477a5c29d18173db40bf0315a
Author: Hugh McMaster <hugh mcmaster outlook com>
Date:   Wed Jul 31 20:45:35 2019 +1000

    xslt-config.in: Fix broken --prefix=DIR support
    
    Passing --prefix=DIR to `configure' is currently ignored.

 xslt-config.in | 2 ++
 1 file changed, 2 insertions(+)
---
diff --git a/xslt-config.in b/xslt-config.in
index 5b885854..1d376b66 100644
--- a/xslt-config.in
+++ b/xslt-config.in
@@ -39,6 +39,8 @@ while test $# -gt 0; do
     case "$1" in
     --prefix=*)
        prefix=$optarg
+        includedir=${prefix}/include
+        libdir=${prefix}/lib
        if test $exec_prefix_set = no ; then
            exec_prefix=$optarg
        fi