fix: determine legacy variant after determining compiler version #404

Job	Run time
Syntax Check - GCC C++03 Linux No STL (ubuntu-22.04)	30s
Syntax Check - GCC C++03 Linux STL (ubuntu-22.04)	32s
Syntax Check - GCC C++11 Linux No STL (ubuntu-22.04)	50s
Syntax Check - GCC C++11 Linux No STL Force C++03 (ubuntu-22.04)	49s
Syntax Check - GCC C++11 Linux STL (ubuntu-22.04)	55s
Syntax Check - GCC C++11 Linux STL Force C++03 (ubuntu-22.04)	54s
Syntax Check - GCC C++14 Linux No STL (ubuntu-22.04)	1m 7s
Syntax Check - GCC C++14 Linux No STL Force C++03 (ubuntu-22.04)	58s
Syntax Check - GCC C++14 Linux STL (ubuntu-22.04)	1m 0s
Syntax Check - GCC C++14 Linux STL Force C++03 (ubuntu-22.04)	55s
Syntax Check - GCC C++17 Linux No STL (ubuntu-22.04)	1m 2s
Syntax Check - GCC C++17 Linux No STL Force C++03 (ubuntu-22.04)	1m 4s
Syntax Check - GCC C++17 Linux STL (ubuntu-22.04)	1m 17s
Syntax Check - GCC C++17 Linux STL Force C++03 (ubuntu-22.04)	1m 17s
Syntax Check - GCC C++20 Linux No STL (ubuntu-22.04)	1m 29s
Syntax Check - GCC C++20 Linux No STL Force C++03 (ubuntu-22.04)	1m 29s
Syntax Check - GCC C++20 Linux STL (ubuntu-22.04)	1m 59s
Syntax Check - GCC C++20 Linux STL Force C++03 (ubuntu-22.04)	1m 57s
	20m 4s

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