Attempting to generate modules within Gen 8.6 and get the error: 

"CA Gen Build Tool Compose
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Exception caught: java.lang.RuntimeException:*** OPT.VSVERSION contains an unknown value () or the specified Visual Studio compiler is not installed.

Compose Failed"

Release : 8.6

Component : CA Gen Workstation Toolset and Build Tool

The error from the .out file for the build of the module is "Exception caught: java.lang.RuntimeException:*** OPT.VSVERSION contains an unknown value () or the specified Visual Studio compiler is not installed."

The value with the Build Tool Profile Manager token OPT.VSVERSION is defaulted to VS140.  The value (VS140) corresponds to the install of VS2015 on this machine.  You will get the above error if you have an invalid value for the token, VS140 is valid... OR the value does not match the version of Visual Studio installed.   The value VS140 corresponds to an install of MS VS2015.  While the value VS150 corresponds to MS VS2017.

Gen r8.6 is certified/supported for:

Per the technical requirements:

https://techdocs.broadcom.com/content/broadcom/techdocs/us/en/ca-mainframe-software/devops/ca-gen/8-6/technical-requirements/third-party-software-version.html

For Reference:  The OPT.VSVERSION value for MS VS2015 is VS140 and for VS2017 it is VS150. 

CA Gen 8.6 Build Tool token OPT.VSVERSION value when using Microsoft Visual Studio 2017