Ubuntu 16.04 being deprecated on Actions build runners

[michaeltryby]

Deprecation effective September, 2021

[michaeltryby]

Upgrading to 18.04 causes an undefined symbol error at runtime while evaluating tests.

2526  Test project /home/runner/work/Stormwater-Management-Model/Stormwater-Management-
Model/build

2527  Start 1: test_lid
2528  1/3 Test #1: test_lid .........................***Failed    0.00 sec

2529  /home/runner/work/Stormwater-Management-Model/Stormwater-Management-Model/
build/bin/test_lid: symbol lookup error: /home/runner/work/Stormwater-Management-Model/
Stormwater-Management-Model/build/bin/test_lid: undefined symbol: swmm_getLidCParam

2530
2531  Start 2: test_output
2532  2/3 Test #2: test_output ......................   Passed    0.01 sec
2533  Start 3: test_solver
2534  3/3 Test #3: test_solver ......................***Failed    0.00 sec

2535  /home/runner/work/Stormwater-Management-Model/Stormwater-Management-Model/
build/bin/test_solver: symbol lookup error: /home/runner/work/Stormwater-Management-Model/
Stormwater-Management-Model/build/bin/test_solver: undefined symbol: swmm_setNodePollut

2536  Errors while running CTest

This may be related to rpath issue when running tests in the build tree with no install. Rpaths are set during install.

[michaeltryby]

One potential solution would be to static link swmm5.so when building tests. This would involve refactoring the CMakeLists to optionally build static or dynamic libraries based on developer preference.

[abhiramm7]

Addressed in #372. https://github.com/OpenWaterAnalytics/Stormwater-Management-Model/blob/51ca3deaeea15f53ae7df842ba5de0171130d597/.github/workflows/build-test.yml#L41