util: Unify implementations of qemu_memalign()

util: Unify implementations of qemu_memalign()

We implement qemu_memalign() in both oslib-posix.c and oslib-win32.c,
but the two versions are essentially the same: they call
qemu_try_memalign(), and abort() after printing an error message if
it fails.  The only difference is that the win32 version prints the
GetLastError() value whereas the POSIX version prints
strerror(errno).  However, this is a bug in the win32 version: in
commit dfbd0b873a85021 in 2020 we changed the implementation of
qemu_try_memalign() from using VirtualAlloc() (which sets the
GetLastError() value) to using _aligned_malloc() (which sets errno),
but didn't update the error message to match.

Replace the two separate functions with a single version in a
new memalign.c file, which drops the unnecessary extra qemu_oom_check()
function and instead prints a more useful message including the
requested size and alignment as well as the errno string.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20220226180723.1706285-4-peter.maydell@linaro.org
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>