[librsvg/wip/davidk/gtk-doc-configure] build: Fix gtk-doc check

[David King <davidk src gnome org>]

commit 34fcf8a6055d6a72752bd931a280418ee4314fdd
Author: David King <amigadave amigadave com>
Date:   Fri May 13 10:07:05 2022 +0100

    build: Fix gtk-doc check
    
    https://gitlab.gnome.org/GNOME/librsvg/-/issues/866

 configure.ac | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)
---
diff --git a/configure.ac b/configure.ac
index c3b1ff341..2d16e6d33 100644
--- a/configure.ac
+++ b/configure.ac
@@ -129,11 +129,11 @@ AC_ARG_ENABLE([gtk-doc],
 
 AS_IF([test "x$enable_gtk_doc" != xno],
       [AC_CHECK_TOOL(GI_DOCGEN, [gi-docgen], [no])
-       AS_IF([test "x$GI_DOCGEN" = no],
+       AS_IF([test "x$GI_DOCGEN" = xno],
              [AS_CASE(["$enable_gtk_doc"],
                       [yes], [AC_MSG_ERROR([gi-docgen not found - cannot build docs])],
                       [auto], [AC_MSG_WARN([gi-docgen not found - not building docs])])
-              enable_gtk_doc=no]
+              enable_gtk_doc=no],
              [enable_gtk_doc=yes])])
 AM_CONDITIONAL(ENABLE_GTK_DOC, [test "x$enable_gtk_doc" = xyes])