Mention `--incompatible_disallow_empty_glob` in the error message.

After a flag flip, some users could be surprised by the error. Mentioning the flag name will let them disable it or easily find information about it.

https://github.com/bazelbuild/bazel/issues/8195

RELNOTES: None.
PiperOrigin-RevId: 321747511
diff --git a/src/test/java/com/google/devtools/build/lib/skyframe/PackageFunctionTest.java b/src/test/java/com/google/devtools/build/lib/skyframe/PackageFunctionTest.java
index b8e545a..98eec33 100644
--- a/src/test/java/com/google/devtools/build/lib/skyframe/PackageFunctionTest.java
+++ b/src/test/java/com/google/devtools/build/lib/skyframe/PackageFunctionTest.java
@@ -1006,7 +1006,8 @@
     pkg = validPackage(skyKey);
     assertThat(pkg.containsErrors()).isTrue();
     String expectedEventString =
-        "glob pattern '*.foo' didn't match anything, but allow_empty is set to False";
+        "glob pattern '*.foo' didn't match anything, but allow_empty is set to False (the "
+            + "default value of allow_empty can be set with --incompatible_disallow_empty_glob).";
     MoreAsserts.assertContainsEvent(pkg.getEvents(), expectedEventString);
     assertContainsEvent(expectedEventString);
   }
@@ -1039,7 +1040,8 @@
     pkg = validPackage(skyKey);
     assertThat(pkg.containsErrors()).isTrue();
     String expectedEventString =
-        "glob pattern '*.foo' didn't match anything, but allow_empty is set to False";
+        "glob pattern '*.foo' didn't match anything, but allow_empty is set to False (the "
+            + "default value of allow_empty can be set with --incompatible_disallow_empty_glob).";
     MoreAsserts.assertContainsEvent(pkg.getEvents(), expectedEventString);
     assertContainsEvent(expectedEventString);
   }
@@ -1055,7 +1057,8 @@
     Package pkg = validPackage(skyKey);
     assertThat(pkg.containsErrors()).isTrue();
     String expectedEventString =
-        "glob pattern '*.foo' didn't match anything, but allow_empty is set to False";
+        "glob pattern '*.foo' didn't match anything, but allow_empty is set to False (the "
+            + "default value of allow_empty can be set with --incompatible_disallow_empty_glob).";
     MoreAsserts.assertContainsEvent(pkg.getEvents(), expectedEventString);
     assertContainsEvent(expectedEventString);
 
@@ -1088,7 +1091,8 @@
     Package pkg = validPackage(skyKey);
     assertThat(pkg.containsErrors()).isTrue();
     String expectedEventString =
-        "glob pattern '*.foo' didn't match anything, but allow_empty is set to False";
+        "glob pattern '*.foo' didn't match anything, but allow_empty is set to False (the "
+            + "default value of allow_empty can be set with --incompatible_disallow_empty_glob).";
     MoreAsserts.assertContainsEvent(pkg.getEvents(), expectedEventString);
     assertContainsEvent(expectedEventString);
 
@@ -1118,7 +1122,8 @@
     Package pkg = validPackage(skyKey);
     assertThat(pkg.containsErrors()).isTrue();
     String expectedEventString =
-        "all files in the glob have been excluded, but allow_empty is set to False.";
+        "all files in the glob have been excluded, but allow_empty is set to False (the "
+            + "default value of allow_empty can be set with --incompatible_disallow_empty_glob).";
     MoreAsserts.assertContainsEvent(pkg.getEvents(), expectedEventString);
     assertContainsEvent(expectedEventString);
 
@@ -1155,7 +1160,8 @@
     Package pkg = validPackage(skyKey);
     assertThat(pkg.containsErrors()).isTrue();
     String expectedEventString =
-        "all files in the glob have been excluded, but allow_empty is set to False.";
+        "all files in the glob have been excluded, but allow_empty is set to False (the "
+            + "default value of allow_empty can be set with --incompatible_disallow_empty_glob).";
     MoreAsserts.assertContainsEvent(pkg.getEvents(), expectedEventString);
     assertContainsEvent(expectedEventString);
 
@@ -1183,7 +1189,8 @@
     Package pkg = validPackage(skyKey);
     assertThat(pkg.containsErrors()).isTrue();
     String expectedEventString =
-        "glob pattern '*.foo' didn't match anything, but allow_empty is set to False";
+        "glob pattern '*.foo' didn't match anything, but allow_empty is set to False (the "
+            + "default value of allow_empty can be set with --incompatible_disallow_empty_glob).";
     MoreAsserts.assertContainsEvent(pkg.getEvents(), expectedEventString);
     assertContainsEvent(expectedEventString);
 
@@ -1216,7 +1223,8 @@
     Package pkg = validPackage(skyKey);
     assertThat(pkg.containsErrors()).isTrue();
     String expectedEventString =
-        "glob pattern '*.foo' didn't match anything, but allow_empty is set to False";
+        "glob pattern '*.foo' didn't match anything, but allow_empty is set to False (the "
+            + "default value of allow_empty can be set with --incompatible_disallow_empty_glob).";
     MoreAsserts.assertContainsEvent(pkg.getEvents(), expectedEventString);
     assertContainsEvent(expectedEventString);