apps/include/opt.h: improve coding style #1224

Job	Run time
compiler (gcc-7, ubuntu-20.04)	4m 16s
compiler (gcc-8, ubuntu-20.04)	4m 25s
compiler (gcc-9, ubuntu-20.04)	4m 38s
compiler (gcc-10, ubuntu-20.04)	4m 22s
compiler (gcc-11, ubuntu-22.04)	4m 35s
compiler (gcc-12, ubuntu-22.04)	4m 59s
compiler (gcc-13, ubuntu-22.04, ubuntu-toolchain-r/test)	7m 3s
compiler (clang-6.0, ubuntu-20.04)	4m 39s
compiler (clang-7, ubuntu-20.04)	4m 40s
compiler (clang-8, ubuntu-20.04)	4m 42s
compiler (clang-9, ubuntu-20.04)	5m 1s
compiler (clang-10, ubuntu-20.04)	4m 46s
compiler (clang-11, ubuntu-20.04)	4m 53s
compiler (clang-12, ubuntu-20.04)	4m 43s
compiler (clang-13, ubuntu-22.04)	4m 58s
compiler (clang-14, ubuntu-22.04)	5m 0s
compiler (clang-15, ubuntu-22.04, jammy)	4m 57s
compiler (clang-16, ubuntu-22.04, jammy)	5m 4s
compiler (clang-17, ubuntu-22.04, jammy)	5m 5s
	1h 32m 46s

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