Scan-build improvements

[bigbrett]

• limits scan-build to only running on unit test suite (no reduction in coverage since all targets wildcard all source files anyway)
• uses --exclude flag to scan-build to ignore wolfCrypt and wolfSSL source files from analysis
• adds -j flag for parallel make

These changes should dramatically speed up the scan-build CI job and prevent issues in wolfCrypt from breaking wolfHSM CI

[miyazakh]

Thanks. It seems that make -j is the most effective. In my environment, the --exclude option does not seem to work, as shown by the failure in wolfcrypt when running make -j SCAN=1 -C tools/whnvmtool/.