update-distcc-symlinks: create symlinks in $prefix

distccd looks for approved compilers in $prefix/lib/distcc.
However update-distcc-symlinks always creates symlinks in /usr/lib.
Thus if distcc is installed in a custom directory (`--prefix=/opt`,
or `--prefix=$HOME`) distccd will refuse compilation jobs even
after running `update-distcc-symlinks`.

This patch adjusts `update-distcc-symlinks` so it creates
symlinks in $prefix/lib/distcc. As a side effect it's possible
to use `update-distcc-symlinks` without root permissions.

Related: #431

Makefile.in

@@ -515,7 +515,9 @@ lsdistcc@EXEEXT@: $(lsdistcc_obj)
 	$(CC) $(CFLAGS) $(LDFLAGS) -o $@ $(lsdistcc_obj) $(LIBS)
 
 update-distcc-symlinks: $(update_distcc_symlinks_PY)
-	cp $< $@
+	sed -e "s;\@prefix\@;${prefix};g" $< > $@.tmp
+	chmod +x $@.tmp
+	mv $@.tmp $@
 
 h_exten@EXEEXT@: $(h_exten_obj)
 	$(CC) $(CFLAGS) $(LDFLAGS) -o $@ $(h_exten_obj) $(LIBS)

update-distcc-symlinks.py

@@ -2,7 +2,7 @@
 
 import subprocess, string, os, stat, re
 
-distcc_dir = "/usr/lib/distcc"
+distcc_dir = "@prefix@/lib/distcc"
 gcc_dir = "/usr/lib/gcc"
 gcccross_dir = "/usr/lib/gcc-cross"
 old_symlinks = set()