avoid an error from configure by not doing a cat on a file that doesn't exist

git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@37284 65c4cc65-6c06-0410-ace0-fbb531ad65f3

configure

@@ -1,5 +1,5 @@
 #! /bin/sh
-# From configure.ac Revision: 37105 .
+# From configure.ac Revision: 37278 .
 # Guess values for system-dependent variables and create Makefiles.
 # Generated by GNU Autoconf 2.59e.
 #
@@ -16428,7 +16428,9 @@ if test "${USE_IMAP_TK}" != "no"; then
    echo -n "checking for UW IMAP Toolkit c-client library... "
    saved_cppflags="${CPPFLAGS}"
    saved_libs="${LIBS}"
-   imap_ldflags=`cat ${IMAP_TK_DIR}/c-client/LDFLAGS`
+   if test -f ${IMAP_TK_DIR}/c-client/LDFLAGS ; then
+      imap_ldflags=`cat ${IMAP_TK_DIR}/c-client/LDFLAGS`
+   fi
    CPPFLAGS="${CPPFLAGS} -I${IMAP_TK_DIR}/c-client"
    LIBS="${LIBS} ${IMAP_TK_DIR}/c-client/c-client.a "`echo ${imap_ldflags}`
    cat >conftest.$ac_ext <<_ACEOF

configure.ac

@@ -341,7 +341,9 @@ if test "${USE_IMAP_TK}" != "no"; then
    echo -n "checking for UW IMAP Toolkit c-client library... "
    saved_cppflags="${CPPFLAGS}"
    saved_libs="${LIBS}"
-   imap_ldflags=`cat ${IMAP_TK_DIR}/c-client/LDFLAGS`
+   if test -f ${IMAP_TK_DIR}/c-client/LDFLAGS ; then
+      imap_ldflags=`cat ${IMAP_TK_DIR}/c-client/LDFLAGS`
+   fi
    CPPFLAGS="${CPPFLAGS} -I${IMAP_TK_DIR}/c-client"
    LIBS="${LIBS} ${IMAP_TK_DIR}/c-client/c-client.a "`echo ${imap_ldflags}`
    AC_LINK_IFELSE(