Make 'packed' have better cross platform functionality #527

Job	Run time
Syntax Check - Clang C++03 Linux No STL (ubuntu-22.04)	27s
Syntax Check - Clang C++03 Linux STL (ubuntu-22.04)	31s
Syntax Check - Clang C++11 Linux No STL (ubuntu-22.04)	34s
Syntax Check - Clang C++11 Linux No STL Force C++03 (ubuntu-22.04)	33s
Syntax Check - Clang C++11 Linux STL (ubuntu-22.04)	38s
Syntax Check - Clang C++11 Linux STL Force C++03 (ubuntu-22.04)	47s
Syntax Check - Clang C++14 Linux No STL (ubuntu-22.04)	41s
Syntax Check - Clang C++14 Linux STL (ubuntu-22.04)	45s
Syntax Check - Clang C++14 Linux No STL Force C++03 (ubuntu-22.04)	48s
Syntax Check - Clang C++17 Linux No STL (ubuntu-22.04)	1m 12s
Syntax Check - Clang C++14 Linux STL Force C++03 (ubuntu-22.04)	46s
Syntax Check - Clang C++17 Linux STL (ubuntu-22.04)	55s
Syntax Check - Clang C++17 Linux STL Force C++03 (ubuntu-22.04)	52s
Syntax Check - Clang C++17 Linux No STL Force C++03 (ubuntu-22.04)	44s
Syntax Check - Clang C++20 Linux No STL (ubuntu-22.04)	1m 0s
Syntax Check - Clang C++20 Linux No STL Force C++03 (ubuntu-22.04)	1m 6s
Syntax Check - Clang C++20 Linux STL (ubuntu-22.04)	1m 23s
Syntax Check - Clang C++20 Linux STL Force C++03 (ubuntu-22.04)	1m 28s
	15m 10s

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