Fix configure flags in evergreen.yml for failing PPC tests

format-stress-sanitizer-smoke-ppc-test failed on ~ Ubuntu 18.04 PPC

Host: ubuntu1804-ppc-7.pic.build.10gen.cc
Project: WiredTiger (develop)
Commit: diff: WT-5571 add enable-strict on all configurations, use ADD_CFLAGS for adding to compiler flags (#5894)

Also, fix the PATH on static-wt-build-test task, otherwise could potentially get a g++ from /bin or elsewhere. | 23 Jul 20 13:47 UTC
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