fix: determine legacy variant after determining compiler version #405

Job	Run time
Syntax Check - Clang C++03 Linux No STL (ubuntu-22.04)	44s
Syntax Check - Clang C++03 Linux STL (ubuntu-22.04)	45s
Syntax Check - Clang C++11 Linux No STL (ubuntu-22.04)	1m 19s
Syntax Check - Clang C++11 Linux No STL Force C++03 (ubuntu-22.04)	1m 14s
Syntax Check - Clang C++11 Linux STL (ubuntu-22.04)	1m 17s
Syntax Check - Clang C++11 Linux STL Force C++03 (ubuntu-22.04)	1m 12s
Syntax Check - Clang C++14 Linux No STL (ubuntu-22.04)	1m 16s
Syntax Check - Clang C++14 Linux No STL Force C++03 (ubuntu-22.04)	1m 10s
Syntax Check - Clang C++14 Linux STL (ubuntu-22.04)	1m 21s
Syntax Check - Clang C++14 Linux STL Force C++03 (ubuntu-22.04)	1m 20s
Syntax Check - Clang C++17 Linux STL (ubuntu-22.04)	1m 58s
Syntax Check - Clang C++17 Linux No STL (ubuntu-22.04)	1m 35s
Syntax Check - Clang C++17 Linux No STL Force C++03 (ubuntu-22.04)	1m 28s
Syntax Check - Clang C++17 Linux STL Force C++03 (ubuntu-22.04)	1m 50s
Syntax Check - Clang C++20 Linux No STL (ubuntu-22.04)	2m 7s
Syntax Check - Clang C++20 Linux No STL Force C++03 (ubuntu-22.04)	2m 8s
Syntax Check - Clang C++20 Linux STL (ubuntu-22.04)	2m 34s
Syntax Check - Clang C++20 Linux STL Force C++03 (ubuntu-22.04)	2m 36s
	27m 54s

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