[libsoup/wip/tpopela/negotiate] configure - Improve how the GSSAPI enabled build is detected

[Tomas Popela <tpopela src gnome org>]

commit 2f3690cde8b83227e6b3c4e02091d56077766f13
Author: Tomas Popela <tpopela redhat com>
Date:   Tue Feb 16 16:02:55 2016 +0100

    configure - Improve how the GSSAPI enabled build is detected
    
    Add the with-gssapi option that's auto enabled unless we are on Windows. Also
    the with-krb5-config was added to specify a path to the krb5-config binary.

 configure.ac |   29 +++++++++++++++++++++--------
 1 files changed, 21 insertions(+), 8 deletions(-)
---
diff --git a/configure.ac b/configure.ac
index 43a2fdb..2425336 100644
--- a/configure.ac
+++ b/configure.ac
@@ -324,14 +324,27 @@ AX_CODE_COVERAGE
 dnl **********************
 dnl *** GSSAPI support ***
 dnl **********************
-AC_PATH_PROG([KRB5_CONFIG], krb5-config, none, $PATH:/usr/kerberos/bin)
-if test "x$KRB5_CONFIG" != "xnone"; then
-    KRB5_LIBS="`${KRB5_CONFIG} --libs gssapi`"
-    KRB5_CFLAGS="`${KRB5_CONFIG} --cflags gssapi`"
-    AC_SUBST(KRB5_CFLAGS)
-    AC_SUBST(KRB5_LIBS)
-    if test "$KRB5_CONFIG" != none; then
-        AC_DEFINE(LIBSOUP_HAVE_GSSAPI, 1, [Whether or not gssapi libs are available])
+AC_ARG_WITH(gssapi,
+           AS_HELP_STRING([--with-gssapi],
+           [Build with GSSAPI support [default=auto]]),
+           [if test $os_win32 = yes; then gssapi="no"; else gssapi="yes"; fi])
+
+if test "$with_gssapi" != "no"; then
+    AC_ARG_WITH(krb5-config,
+               AS_HELP_STRING([--with-krb5-config=PATH],[Where to look for krb5-config, path points to 
krb5-config installation (default: /usr/kerberos/bin/)]),
+               KRB5_CONFIG="$withval",
+               [AC_PATH_PROGS(KRB5_CONFIG, krb5-config, no, ${PATH}:/usr/kerberos/bin)])
+
+    if test "$KRB5_CONFIG" != "no"; then
+       KRB5_LIBS="`${KRB5_CONFIG} --libs gssapi`"
+       KRB5_CFLAGS="`${KRB5_CONFIG} --cflags gssapi`"
+       AC_SUBST(KRB5_CFLAGS)
+       AC_SUBST(KRB5_LIBS)
+       if test "$KRB5_CONFIG" != none; then
+           AC_DEFINE(LIBSOUP_HAVE_GSSAPI, 1, [Whether or not GSSAPI libs are available])
+       fi
+    else
+       AC_MSG_ERROR([GSSAPI support requested but failed to found krb5-config. Try to set KRB5_CONFIG.])
     fi
 fi