build break in graph_parallel - because of the removed libs/system/build/Jamfile.v2 #43

Problem comes using Boost 1.89.

The build error is this:

error: Unable to find file or target named
error: 'libs/system/build//boost_system'
error: referred to from project at error:
    '../libs/graph_parallel/test'
error: could not resolve project reference
    'libs/system/build'

I know that boost_system is header-only since Boost 1.69.
Also the libs/system/build/Jamfile.v2 exists in Boost 1.88, for compatibility reasons, I presume, but now it has been removed in Boost 1.89.

So the reference of
<library>../../system/build//boost_system
in
libs/graph_parallel/test/Jamfile.v2
now points to a nonexistent target.

I found two such invalid references in Boost 1.89:

libs/graph_parallel/test/Jamfile.v2:12:    : requirements <library>../build//boost_graph_parallel <library>../../system/build//boost_system ;
libs/graph_parallel/example/Jamfile.v2:9:    <library>../../system/build//boost_system

Summary: libs/system/build/Jamfile.v2 has been removed, without checking dependent Jamfiles.
But any automated non-regression build covering graph_parallel/test would have caught it instantly :(