whereami: Use SOURCE_DIR variable #253

Job	Run time
Code formatting	12s
Exercise Python examples on ubuntu-latest	1m 25s
Check Ruby Samples ubuntu-latest	1m 52s
Check Ruby Samples macos-13	1m 43s
Build Windows fetch	2m 44s
Build ubuntu-20.04 gcc os	1m 6s
Build Windows vcpkg	7m 26s
Build ubuntu-20.04 gcc fetch	1m 29s
Build ubuntu-20.04 gcc vcpkg	4m 17s
Build ubuntu-20.04 clang os	1m 8s
Build ubuntu-20.04 clang fetch	2m 16s
Build ubuntu-20.04 clang vcpkg	4m 45s
Build macos-latest gcc os	1m 2s
Build macos-latest gcc fetch	1m 17s
Build macos-latest gcc vcpkg	1m 28s
Build macos-latest clang os	1m 9s
Build macos-latest clang fetch	1m 10s
Build macos-latest clang vcpkg	1m 12s
	37m 41s

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