WebAssembly: build both the multithreaded and non-multithreaded versions in parallel, optimize the workflows a bit #13066

Job	Run time
Code style check / Code style check	5s
MSVC / MSVC (SDL2 x86)	3m 34s
MSVC / MSVC (SDL2 x64)	3m 43s
CodeChecker / CodeChecker	32m 3s
IWYU / IWYU	4m 11s
SonarCloud Analyzer / SonarCloud Analyzer	0s
CMake / CMake (Linux SDL2)	2m 53s
CMake / CMake (macOS SDL2)	2m 29s
CMake / CMake (macOS SDL2 App Bundle)	1m 39s
Android / Android	11m 29s
CMake / CMake (Windows SDL2)	4m 59s
Make / Make (Linux x86-64 SDL2 Release)	2m 39s
Make / Make (Linux x86-64 SDL2 Debug)	3m 21s
Make / Make (Linux ARM64 SDL2 Release)	2m 16s
Make / Make (Nintendo Switch)	3m 10s
Make / Make (PS Vita)	11m 7s
Make / Make (Linux ARM64 SDL2 Debug)	3m 0s
Make / Make (macOS SDL2)	2m 56s
Make / Make (macOS SDL2 App Bundle)	1m 34s
Make / Make (Emscripten)	6m 52s
Make / Make (Emscripten Multithreaded)	6m 55s
	1h 50m 55s

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