Add quoted case to quoting test

When ${@}, the current behavior should be preserved

Signed-off-by: Rudi Grinberg <rudi.grinberg@gmail.com>

test/blackbox-tests/test-cases/quoting/bad/dune

@@ -0,0 +1,3 @@
+(rule
+ ((targets (x y))
+  (action (with-stdout-to ${@} (echo foo)))))

test/blackbox-tests/test-cases/quoting/dune

@@ -1,3 +0,0 @@
-(rule
- ((targets (x y))
-  (action (with-stdout-to ${@} (echo foo)))))

test/blackbox-tests/test-cases/quoting/good/dune

@@ -0,0 +1,3 @@
+(rule
+ ((targets (s t))
+  (action (with-stdout-to "${@}" (echo foo)))))

test/blackbox-tests/test-cases/quoting/run.t

@@ -1,9 +1,15 @@
 This behavior is surprising, we should get an error about the fact
 that ${@} is not quoted and doesn't contain exactly 1 element
 
-  $ dune build x
+  $ dune build --root bad x 2>&1 | grep -v Entering
   Error: Rule failed to generate the following targets:
   - x
   - y
-  [1]
 
+
+The targets should only be interpreted as a single path when quoted
+
+  $ dune build --root good s 2>&1 | grep -v Entering
+  Error: Rule failed to generate the following targets:
+  - s
+  - t