With JDK-8169925, jlink creates the JDK images and creates symbolic links to COPYRIGHT and LICENSE files in legal/java.base directory on the platforms that support symlinks.

$ ls -l jdk-9/legal/java.base/
total 56
drwxrwxr-x 9 mlchung wheel 306 Dec 20 11:46 ./
drwxrwxr-x 81 mlchung wheel 2754 Dec 20 11:46 ../
-r--r--r-- 1 mlchung wheel 3244 Dec 20 11:46 COPYRIGHT
-r--r--r-- 1 mlchung wheel 40 Dec 20 11:46 LICENSE
-r--r--r-- 1 mlchung wheel 1444 Dec 20 11:46 aes.md
-r--r--r-- 1 mlchung wheel 1582 Dec 20 11:46 asm.md
-r--r--r-- 1 mlchung wheel 1983 Dec 20 11:46 cldr.md
-r--r--r-- 1 mlchung wheel 2934 Dec 20 11:46 icu.md
-r--r--r-- 1 mlchung wheel 1010 Dec 20 11:46 zlib.md

$ ls -l jdk-9/legal/java.desktop/
total 112
lrwxr-xr-x 1 mlchung wheel 22 Dec 20 11:57 COPYRIGHT@ -> ../java.base/COPYRIGHT
lrwxr-xr-x 1 mlchung wheel 20 Dec 20 11:57 LICENSE@ -> ../java.base/LICENSE

The above are the expected symlinks.

When it builds with installer enabled, the bundle that installer build generates changes the symbolic link to an incorrect and non-existent file:
   legal/java.desktop/COPYRIGHT -> jdk-9/../java.base/COPYRIGHT

Looks to me that installer does something special to symbolic links in the image but causes the symlinks to be incorrect.

$ ls -l legal/java.desktop/
total 56
drwxrwxr-x 2 mlchung mlchung 4096 Dec 20 11:55 ./
drwxrwxr-x 99 mlchung mlchung 4096 Dec 20 11:55 ../
lrwxrwxrwx 1 mlchung mlchung 28 Dec 19 11:36 COPYRIGHT -> jdk-9/../java.base/COPYRIGHT
lrwxrwxrwx 1 mlchung mlchung 26 Dec 19 11:36 LICENSE -> jdk-9/../java.base/LICENSE
-r--r--r-- 1 mlchung mlchung 181 Dec 19 11:36 colorimaging.md
-r--r--r-- 1 mlchung mlchung 1157 Dec 19 11:36 fontconfig.md
-r--r--r-- 1 mlchung mlchung 1138 Dec 19 11:36 giflib.md
-r--r--r-- 1 mlchung mlchung 2779 Dec 19 11:36 harfbuzz.md
-r--r--r-- 1 mlchung mlchung 3966 Dec 19 11:36 jpeg.md
-r--r--r-- 1 mlchung mlchung 1177 Dec 19 11:36 lcms.md
-r--r--r-- 1 mlchung mlchung 3982 Dec 19 11:36 libpng.md
-r--r--r-- 1 mlchung mlchung 1191 Dec 19 11:36 mesa3d.md
-r--r--r-- 1 mlchung mlchung 1158 Dec 19 11:36 opengl.md
-r--r--r-- 1 mlchung mlchung 10084 Dec 19 11:36 xwindows.md