configure: move ctags checks here from mkproto.sh

Makefile.conf.in

@@ -16,3 +16,6 @@ XLD_IMB_OPT := @XLD_IMB_OPT@
 CROSS_STRIP := @CROSS_STRIP@
 
 CROSS_ASFLAGS := @CROSS_ASFLAGS@
+
+CTAGS := @CTAGS@
+RTAGS := @RTAGS@

configure.ac

@@ -162,4 +162,13 @@ if test -z "$CROSS_STRIP"; then
   AC_MSG_ERROR([cross-strip not found])
 fi
 
+AC_CHECK_PROGS([CTAGS], [uctags ctags])
+AC_CHECK_PROGS([RTAGS], [ureadtags readtags])
+if test -z "$CTAGS" -o -z "$RTAGS"; then
+  AC_MSG_ERROR([universal-ctags not installed])
+fi
+if ! $CTAGS --version | grep "Universal Ctags" >/dev/null; then
+  AC_MSG_ERROR([bsd ctags do not suit, install universal-ctags])
+fi
+
 AC_OUTPUT

src/libc/dj64/parsers/mkproto.sh

@@ -8,25 +8,9 @@ if [ $# -lt 5 ]; then
     exit 1
 fi
 
-if ! which uctags >/dev/null 2>&1; then
-    if ! which ctags >/dev/null 2>&1; then
-	echo "universal-ctags not installed"
-	exit 1
-    fi
-    if ! ctags -L /dev/null -f /dev/null; then
-	if [ "`uname -s`" = "FreeBSD" ]; then
-	    echo "bsd ctags do not suit, install universal-ctags"
-	    exit 1
-	else
-	    # https://bugs.launchpad.net/ubuntu/+source/coreutils/+bug/2069483
-	    echo "ctags reported failure, running on ubuntu Focal?"
-	fi
-    fi
-    RTAGS=readtags
-    CTAGS=ctags
-else
-    RTAGS=ureadtags
-    CTAGS=uctags
+if test -z "$CTAGS" -o test -z "$RTAGS"; then
+    echo "universal-ctags not installed"
+    exit 1
 fi
 
 extr_proto() {

src/makefile.inc

@@ -10,6 +10,8 @@ SHELL := bash -o pipefail
 
 # for mkproto.sh
 export CROSS_LD
+export CTAGS
+export RTAGS
 
 export prefix