Handle Spaces in Makefile Parsing

In a Makefile, spaces can be escaped by a preceeding backslash. Rather
than using string.split, iterate through the string keeping track of the
previous character.

Author: gmittert

Sources/tibs/main.swift

@@ -42,7 +42,21 @@ func swiftDepsMerge(output: String, _ files: [String]) {
         exit(1)
       }
 
-      let deps = depStr.split(whereSeparator: { $0.isWhitespace })
+      var deps: [Substring] = []
+      var prev: Character = "."
+      var it = depStr.startIndex
+      var strStart = it
+      while it != depStr.endIndex {
+          let curr = depStr[it]
+          if curr == " " && prev != "\\" {
+              deps.append(depStr[strStart..<it])
+              strStart = depStr.index(after: it)
+          }
+          prev = curr
+          it = depStr.index(after: it)
+      }
+      deps.append(depStr[strStart..<it])
+
       for dep in deps {
         allDeps.insert(dep)
       }