Add comment to document the purpose behind the non-standard handling …

…of the error

Signed-off-by: Talon Bowler <talon.bowler@docker.com>
(cherry picked from commit 366328b)

commands/build.go

@@ -878,6 +878,12 @@ func printResult(f *controllerapi.PrintFunc, res map[string]string) error {
 			}
 		}
 		if lintResults.Error != nil {
+			// Print the error message and the source
+			// Normally, we would use `errdefs.WithSource` to attach the source to the
+			// error and let the error be printed by the handling that's already in place,
+			// but here we want to print the error in a way that's consistent with how
+			// the lint warnings are printed via the `lint.PrintLintViolations` function,
+			// which differs from the default error printing.
 			fmt.Println()
 			lintBuf := bytes.NewBuffer([]byte(lintResults.Error.Message + "\n"))
 			sourceInfo := lintResults.Sources[lintResults.Error.Location.SourceIndex]