gn format: Add 'outputs' to preferred-multiline lists

tools/gn/format_test_data/042.gn

Index: tools/gn/format_test_data/042.gn
diff --git a/tools/gn/format_test_data/042.gn b/tools/gn/format_test_data/042.gn
index 7affa70391c060a912d5237c2f12d0c1140ba03b..b827f29e0704b8ec793955fd7690982593557a22 100644
--- a/tools/gn/format_test_data/042.gn
+++ b/tools/gn/format_test_data/042.gn
@@ -10,6 +10,7 @@ if (true) {
   include_dirs = []
   inputs = []
   ldflags = []
+  outputs = []
   public_deps = []
   sources = []
 } else if (true) {
@@ -23,6 +24,7 @@ if (true) {
   include_dirs = [ "x" ]
   inputs = [ "x" ]
   ldflags = [ "x" ]
+  outputs = [ "x" ]
   public_deps = [ "x" ]
   sources = [ "x" ]
 } else {
@@ -36,6 +38,7 @@ if (true) {
   include_dirs = [ "x", "y", "z"]
   inputs = [ "x", "y", "z"]
   ldflags = [ "x", "y", "z"]
+  outputs = [ "x", "y", "z"]
   public_deps = [ "x", "y", "z"]
   sources = [ "x", "y", "z"]
 }