Breakpoints with multiple sourceFileMap mapping only works for the first mapping, not the second one

Bug type: Debugger

Describe the bug

• OS and Version: Linux Ubunut 18.04
• VS Code Version: 1.60.2
• C/C++ Extension Version: v1.6.0
• Other extensions you installed (and if the issue persists after disabling them): bazel , yes
• A clear and concise description of what the bug is.

I am on a bazel build for a project with multiple workspaces

Therefore I need multiple entries in the sourceFileMap.

The problem is, all breakpoints in sources from the second source file mapping are disabled.
I can step through the code, and the corresponding code is opened in the editor,
but all breakpoints that are not in files from the first source file mapping become disabled/

To Reproduce
Please include a code sample and launch.json configuration.
Steps to reproduce the behavior:

Set a breakpoint in a file from the second mapping, it is ignored

Set a breakpoint in a file from the first mapping, it works

Remove the first mapping, files will not be found, but the breakpoint from the - now first but previously second - breakpoint work

    "version": "0.2.0",
    "configurations": [
        {
            "name": "some_bin",
            "type": "cppdbg",
            "request": "launch",
            "program": "${workspaceFolder}/current_workspace/.bazel/what/ever/some_bin"
            "args": [],
            "stopAtEntry": false,
            "cwd": "${fileDirname}",
            "environment": [],
            "externalConsole": false,
            "MIMode": "gdb",
            "setupCommands": [
                {
                    "description": "Enable pretty-printing for gdb",
                    "text": "-enable-pretty-printing",
                    "ignoreFailures": true
                }
            ],
            "sourceFileMap": {
                // parent bazel workspace == ${workspaceFolder}
                "/proc/self/cwd/external/" : "/home/me/project/",            
               "/proc/self/cwd/" : "/home/me/project/current_workspace/" ,
            }
        }

Interestingly, when I set stopAtEntry to true, the main function is stopped, (a file from the second mapping) but all breakpoints int this file are grey out

Start by reproducing the issue with the provided launch.json configuration and its two sourceFileMap entries under the C++ debugger. Check breakpoint behavior for files in each mapping, including with stopAtEntry enabled. Done means breakpoints in files from the second mapping remain enabled and are hit like those from the first mapping.