Work better with how make/bmake works:

1.  Avoid a cd back into ${.CURDIR} to run mkbuiltins when we know make
    will first cd into ${.OBJDIR}. Keep the cwd to what make sets it to.
2.  Don't tell mkbuiltins where to write to (= ${.OBJDIR}), but where to
    get sources from (= ${.CURDIR}). This to compensate for point 1.

This fixes a problem with bmake's mk files that optimize ${.OBJDIR} to
expand to "." after changing cwd, not taking into account that the
target is pretty much undoing that and not getting the full path to the
object tree anymore.

bin/sh/Makefile

@@ -38,7 +38,7 @@ build-tools: mkinit mknodes mksyntax
 
 .ORDER: builtins.c builtins.h
 builtins.c builtins.h: mkbuiltins builtins.def
-	cd ${.CURDIR}; sh mkbuiltins ${.OBJDIR}
+	sh ${.CURDIR}/mkbuiltins ${.CURDIR}
 
 init.c: mkinit alias.c eval.c exec.c input.c jobs.c options.c parser.c \
 	redir.c trap.c var.c

bin/sh/mkbuiltins

@@ -35,17 +35,17 @@
 # $FreeBSD$
 
 temp=`/usr/bin/mktemp -t ka`
-havejobs=0
-if grep '^#define[	 ]*JOBS[	 ]*1' shell.h > /dev/null
-then	havejobs=1
-fi
 havehist=1
 if [ "X$1" = "X-h" ]; then
 	havehist=0
 	shift
 fi
-objdir=$1
-exec > ${objdir}/builtins.c
+srcdir=$1
+havejobs=0
+if grep '^#define[	 ]*JOBS[	 ]*1' $srcdir/shell.h > /dev/null
+then	havejobs=1
+fi
+exec > builtins.c
 cat <<\!
 /*
  * This file was generated by the mkbuiltins program.
@@ -57,7 +57,7 @@ cat <<\!
 
 !
 awk '/^[^#]/ {if(('$havejobs' || $2 != "-j") && ('$havehist' || $2 != "-h")) \
-    print $0}' builtins.def | sed 's/-[hj]//' > $temp
+    print $0}' $srcdir/builtins.def | sed 's/-[hj]//' > $temp
 echo 'int (*const builtinfunc[])(int, char **) = {'
 awk '/^[^#]/ {	printf "\t%s,\n", $1}' $temp
 echo '};
@@ -74,7 +74,7 @@ awk '{	for (i = 2 ; i <= NF ; i++) {
 echo '	{ NULL, 0, 0 }
 };'
 
-exec > ${objdir}/builtins.h
+exec > builtins.h
 cat <<\!
 /*
  * This file was generated by the mkbuiltins program.