Logging this issue for record purposes.

The javac behaviour change seen exists since JDK 9. One such summary of the change is available here: https://mail.openjdk.org/pipermail/compiler-dev/2016-November/010544.html

Specifying the output directory via the javac "-d" directive should resolve the issue reported.

 mkdir symLinkTest
 cd symLinkTest
 mkdir readOnlyDir
 echo "public class Hello {}" > readOnlyDir/Hello.java
 ln -s readOnlyDir/Hello.java
 chmod 555 readOnlyDir
  
  
  /jdk1.8.0_381/bin/javac Hello.java
     --> Hello.class created in symLinkTest directory


  With JDK 9 or later:

  $ /jdk-11.0.16/bin/javac Hello.java
  Hello.java:1: error: error while writing Hello: /tmp/symLinkTest/readOnlyDir/Hello.class
  public class Hello {}
         ^
  1 error

following works:
$ /jdk-11.0.16/bin/javac -d . Hello.java