The '-XXaltjvm=<path>' option is interpreted by the 'java' launcher to
load a different JVM binary than the default JVM. There is code in
the JVM that has to adapt to the fact that the alternate JVM might
live in a different location than the JAVA_HOME that contains the
'java' launcher.

Unfortunately, the code in the JVM that adapts to the alternate JVM
location is tightly coupled with vestigial "gamma launcher" support.
Once '-XXaltjvm=<path>' and the "gamma launcher" are decoupled,
work on the following bug can proceed:

    JDK-8005262 possible gamma launcher issues