abis/ironclad: define CBAUD for termios.h #3255

Job	Run time
Compile sysdeps (dripos)	2m 13s
Build mlibc (x86_64, mlibc)	3m 33s
Compile sysdeps (lemon)	2m 34s
Compile sysdeps (aero)	2m 20s
Build mlibc (x86_64, mlibc-static)	3m 12s
Compile sysdeps (ironclad)	2m 14s
Build mlibc (x86_64, mlibc-shared)	3m 4s
Compile sysdeps (lyre)	2m 21s
Build mlibc (x86_64, mlibc-ansi-only)	2m 59s
Compile sysdeps (keyronex)	2m 44s
Build mlibc (x86_64, mlibc-headers-only)	2m 35s
Build mlibc (riscv64, mlibc)	3m 42s
Build mlibc (riscv64, mlibc-static)	4m 35s
Build mlibc (riscv64, mlibc-shared)	2m 52s
Build mlibc (riscv64, mlibc-ansi-only)	2m 44s
Build mlibc (riscv64, mlibc-headers-only)	1m 47s
Build mlibc (aarch64, mlibc)	3m 49s
Build mlibc (aarch64, mlibc-static)	3m 4s
Build mlibc (aarch64, mlibc-shared)	3m 10s
Build mlibc (aarch64, mlibc-ansi-only)	2m 55s
Build mlibc (aarch64, mlibc-headers-only)	1m 47s
	1h 0m 14s

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