[configure] fix check for GNU awk/gawk to abort ./configure if missing
It also prints what were comments explaining why gawk is necessary, and
not-in-PATH to help user figure out why it's not found.
Build was mysteriously failing with the old version of this check when gawk
wasn't installed.
diff --git a/configure.ac b/configure.ac
index 63cef65..db36d5e 100755
--- a/configure.ac
+++ b/configure.ac
@@ -21,9 +21,11 @@
AM_INIT_AUTOMAKE(1.6)
AM_CONFIG_HEADER(config.h)
-dnl GNU awk is required for lib/memtype.h made by memtypes.awk.
-dnl BSD awk complains: awk: gensub doesn't support backreferences (subst "\1")
-AC_CHECK_PROG([GAWK],[gawk],[gawk],[/bin/false])
+AC_CHECK_PROG([GAWK],[gawk],[gawk],[not-in-PATH])
+if test "x$GAWK" = "xnot-in-PATH" ; then
+ AC_MSG_ERROR([GNU awk is required for lib/memtype.h made by memtypes.awk.
+BSD awk complains: awk: gensub doesn't support backreferences (subst "\1") ])
+fi
AC_ARG_VAR([GAWK],[GNU AWK])
dnl default is to match previous behavior