exception when mvn build directory is a softlink to actual directory

[243826]

If you are submitting a bug, please include the following:

• summary of problem
  I have softlinked the build dir to another location on the filesystem. I reviewed the function and it seems that ensureParentDirExists could be conservative to first check whether the directory exists before firing the command to create the directories and in turn failing.
• gradle or maven version
• spotless version
  2.40.0
• operating system and version
  linux
• copy-paste your full Spotless configuration block(s), and a link to a public git repo that reproduces the problem if possible
• copy-paste the full content of any console errors emitted by gradlew spotless[Apply/Check] Caused by: java.io.UncheckedIOException: Unable to create parent directory for the index file: /mnt/c/Users/chetan/work/xxxx/yyyy/target/linux/spotless-index at com.diffplug.spotless.maven.incremental.FileIndex.ensureParentDirExists (FileIndex.java:149) at com.diffplug.spotless.maven.incremental.FileIndex.write (FileIndex.java:129) at com.diffplug.spotless.maven.incremental.IndexBasedChecker.close (IndexBasedChecker.java:71) at com.diffplug.spotless.maven.incremental.UpToDateChecker$1.close (UpToDateChecker.java:60) at com.diffplug.spotless.maven.AbstractSpotlessMojo.execute (AbstractSpotlessMojo.java:231) at org.apache.maven.plugin.DefaultBuildPluginManager.executeMojo (DefaultBuildPluginManager.java:126) at org.apache.maven.lifecycle.internal.MojoExecutor.doExecute2 (MojoExecutor.java:328) at org.apache.maven.lifecycle.internal.MojoExecutor.doExecute (MojoExecutor.java:316) at org.apache.maven.lifecycle.internal.MojoExecutor.execute (MojoExecutor.java:212) at org.apache.maven.lifecycle.internal.MojoExecutor.execute (MojoExecutor.java:174) at org.apache.maven.lifecycle.internal.MojoExecutor.access$000 (MojoExecutor.java:75) at org.apache.maven.lifecycle.internal.MojoExecutor$1.run (MojoExecutor.java:162) at org.apache.maven.plugin.DefaultMojosExecutionStrategy.execute (DefaultMojosExecutionStrategy.java:39) at org.apache.maven.lifecycle.internal.MojoExecutor.execute (MojoExecutor.java:159) at org.apache.maven.lifecycle.internal.LifecycleModuleBuilder.buildProject (LifecycleModuleBuilder.java:105) at org.apache.maven.lifecycle.internal.LifecycleModuleBuilder.buildProject (LifecycleModuleBuilder.java:73) at org.apache.maven.lifecycle.internal.builder.singlethreaded.SingleThreadedBuilder.build (SingleThreadedBuilder.java:53) at org.apache.maven.lifecycle.internal.LifecycleStarter.execute (LifecycleStarter.java:118) at org.apache.maven.DefaultMaven.doExecute (DefaultMaven.java:261) at org.apache.maven.DefaultMaven.doExecute (DefaultMaven.java:173) at org.apache.maven.DefaultMaven.execute (DefaultMaven.java:101) ....

If you're just submitting a feature request or question, no need for the above.