Update generate_api_docs.sh #705

Job	Run time
msvc-x64, Release, Shared=ON	5m 20s
msvc-x64, Release, Shared=OFF	5m 42s
clang-x64, Release, Shared=ON	8m 40s
clang-x64, Release, Shared=OFF	8m 40s
msvc-x64, RelWithDebInfo, Shared=ON	6m 18s
msvc-x64, RelWithDebInfo, Shared=OFF	5m 38s
clang-x64, RelWithDebInfo, Shared=ON	9m 35s
clang-x64, RelWithDebInfo, Shared=OFF	9m 10s
msvc-Win32, RelWithDebInfo, Shared=ON	5m 37s
msvc-Win32, RelWithDebInfo, Shared=OFF	5m 30s
clang-Win32, RelWithDebInfo, Shared=ON	9m 25s
clang-Win32, RelWithDebInfo, Shared=OFF	9m 24s
	1h 28m 59s

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