[libxslt] configure.ac: remove useless AC_SUBST

[Nick Wellnhofer <nwellnhof src gnome org>]

commit 11b078b0917a35d28f2e60385a85e2a0a11a5484
Author: David Seifert <soap gentoo org>
Date:   Sat Apr 2 14:30:13 2022 +0200

    configure.ac: remove useless AC_SUBST
    
    * CFLAGS/CPPFLAGS/LDFLAGS are always substituted

 configure.ac | 4 ----
 1 file changed, 4 deletions(-)
---
diff --git a/configure.ac b/configure.ac
index 44147e84..1b7b2c44 100644
--- a/configure.ac
+++ b/configure.ac
@@ -457,10 +457,6 @@ then
 fi
 
 
-AC_SUBST(CFLAGS)
-AC_SUBST(CPPFLAGS)
-AC_SUBST(LDFLAGS)
-
 AC_ARG_WITH(plugins,
 [  --with-plugins          Add plugin extension support (on)])
 if test "$with_plugins" = ""