Move toolchain from /tools to /tools_${arch}

This will allow us to run multiple builds on the same
system at the same time (or at least have them on disk).

Signed-off-by: Michael Tremer <michael.tremer@ipfire.org>

lfs/automake

@@ -32,13 +32,13 @@ DL_FROM    = $(URL_IPFIRE)
 DIR_APP    = $(DIR_SRC)/$(THISAPP)
 TARGET     = $(DIR_INFO)/$(THISAPP)
 
-# Normal build or /tools build.
+# Normal build or $(TOOLS_DIR) build.
 #
 ifeq "$(ROOT)" ""
 	PREFIX = /usr
 	TARGET = $(DIR_INFO)/$(THISAPP)
 else
-	PREFIX = /tools
+	PREFIX = $(TOOLS_DIR)
 	TARGET = $(DIR_INFO)/$(THISAPP)-tools
 endif