[ScopBuilder] Slightly improve code structure [NFCI]

First build the surrounding loops and then build up the polyhedral
structures. Before r326664 we had to mix these updates, clean this
up to improve readability (slightly).

git-svn-id: https://llvm.org/svn/llvm-project/polly/trunk@334412 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Analysis/ScopBuilder.cpp b/lib/Analysis/ScopBuilder.cpp
index be19bd0..48d8b20 100644
--- a/lib/Analysis/ScopBuilder.cpp
+++ b/lib/Analysis/ScopBuilder.cpp
@@ -1537,8 +1537,9 @@
 
   // The ScopStmts now have enough information to initialize themselves.
   for (ScopStmt &Stmt : *scop) {
-    buildDomain(Stmt);
     collectSurroundingLoops(Stmt);
+
+    buildDomain(Stmt);
     buildAccessRelations(Stmt);
 
     if (DetectReductions)