rustbuild: Don't make any directories when enabled

As part of the ./configure step don't create any directories if rustbuild is
enable as rustbuild will take care of everything.

configure

@@ -1327,27 +1327,29 @@ then
     fi
 fi
 
-step_msg "making directories"
+if [ -z "$CFG_ENABLE_RUSTBUILD" ]; then
 
-for i in \
+  step_msg "making directories"
+
+  for i in \
       doc doc/std doc/extra \
       dl tmp dist
-do
+  do
       make_dir $i
-done
+  done
 
-for t in $CFG_HOST
-do
+  for t in $CFG_HOST
+  do
       make_dir $t/llvm
-done
+  done
 
-for t in $CFG_HOST
-do
+  for t in $CFG_HOST
+  do
       make_dir $t/rustllvm
-done
+  done
 
-for t in $CFG_TARGET
-do
+  for t in $CFG_TARGET
+  do
     make_dir $t/rt
     for s in 0 1 2 3
     do
@@ -1361,10 +1363,10 @@ do
         make_dir $t/rt/stage$s/$i
       done
     done
-done
+  done
 
-for h in $CFG_HOST
-do
+  for h in $CFG_HOST
+  do
       for t in $CFG_TARGET
       do
           # host bin dir stage0
@@ -1417,7 +1419,9 @@ do
       make_dir $h/test/codegen
       make_dir $h/test/codegen-units
       make_dir $h/test/rustdoc
-done
+  done
+
+fi
 
 # Configure submodules
 step_msg "configuring submodules"