Use SCRIPT_DIR placeholder in fixtures

Author: stevapple

Fixtures/Scripts/EchoArguments/PackageSyntax.txt

@@ -2,5 +2,5 @@
   "dependencies" : [
 
   ],
-  "sourceFile" : "\/Users\/yr.chen\/Developer\/GSoC\/swift-package-manager\/Fixtures\/Scripts\/EchoArguments\/EchoArguments.swift"
+  "sourceFile" : "SCRIPT_DIR\/EchoArguments.swift"
 }

Fixtures/Scripts/EchoCWD/PackageSyntax.txt

@@ -2,15 +2,15 @@
   "dependencies" : [
     {
       "package" : {
-        "raw" : "name:\"CwdDump\",path:\"\/Users\/yr.chen\/Developer\/GSoC\/swift-package-manager\/Fixtures\/Scripts\/EchoCWD\/cwd-dump\"",
-        "path" : "\/Users\/yr.chen\/Developer\/GSoC\/swift-package-manager\/Fixtures\/Scripts\/EchoCWD\/cwd-dump",
+        "raw" : "name:\"CwdDump\",path:\"SCRIPT_DIR\/cwd-dump\"",
+        "path" : "SCRIPT_DIR\/cwd-dump",
         "name" : "CwdDump"
       },
       "modules" : [
         "CwdDump"
       ]
     }
   ],
-  "sourceFile" : "\/Users\/yr.chen\/Developer\/GSoC\/swift-package-manager\/Fixtures\/Scripts\/EchoCWD\/EchoCWD.swift"
+  "sourceFile" : "SCRIPT_DIR\/EchoCWD.swift"
 }
 

Sources/SPMTestSupport/misc.swift

@@ -267,7 +267,10 @@ private func withPackageSyntax(from file: AbsolutePath, _ body: () throws -> Voi
     try withTemporaryDirectory { path in
         let parser = path.appending(component: "package-syntax-parser")
         try localFileSystem.writeFileContents(parser) {
-            $0.write("cat \(file.toJSON())\n")
+            // Manually escape the separator.
+            let dirname = file.dirname.replacingOccurrences(of: "/", with: "\\/")
+            // Replace placeholder with the real dirpath.
+            $0.write("cat \(file.pathString.spm_shellEscaped()) | sed 's$SCRIPT_DIR$\(dirname)$g' \n")
             $0.flush()
         }
         try localFileSystem.chmod(.executable, path: parser)