configure: higher precedence for $LEMON

diff --git a/m4/psi/psi.m4 b/m4/psi/psi.m4
index 4012ec1c782e5e24d45718a29a6d64a41afbd077..63ed1942ed7cced3ee09dd9d0f5945a7208d8ad3 100644 (file)
--- a/m4/psi/psi.m4
+++ b/m4/psi/psi.m4
@@ -294,7 +294,10 @@ dnl PSI_LEMON()
 dnl Declare $LEMON precious, and check for a `lemon` in $PATH.
 AC_DEFUN(PSI_LEMON, [
        AC_ARG_VAR(LEMON, The lemon parser generator of the SQLite project)
-       AC_PATH_PROG(LEMON, lemon, ./lemon)
+       if test -z "$LEMON"
+       then
+               AC_PATH_PROG(LEMON, lemon, ./lemon)
+       fi
        PHP_SUBST(LEMON)
 ])