resource-query: fix segfault in graphml writer

[trws]

problem: we're indexing the graph with an end iterator for vertices, which is invalid, instead of the current iterator for the edge we need

solution: use the correct iterator

fixes #1289

Also, this adds a new cmake preset called "rpm" to build with the site flags used by the build farm.

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 75.3%. Comparing base (893e2dc) to head (fb7dde8). Report is 3 commits behind head on master.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #1290 +/- ## ====================================== Coverage 75.3% 75.3% ====================================== Files 110 110 Lines 15236 15236 ====================================== + Hits 11482 11486 +4 + Misses 3754 3750 -4 ``` | [Files with missing lines](https://app.codecov.io/gh/flux-framework/flux-sched/pull/1290?dropdown=coverage&src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=flux-framework) | Coverage Δ | | |---|---|---| | [resource/utilities/resource-query.cpp](https://app.codecov.io/gh/flux-framework/flux-sched/pull/1290?src=pr&el=tree&filepath=resource%2Futilities%2Fresource-query.cpp&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=flux-framework#diff-cmVzb3VyY2UvdXRpbGl0aWVzL3Jlc291cmNlLXF1ZXJ5LmNwcA==) | `76.2% <100.0%> (+1.1%)` | :arrow_up: |