I re-read the modified code, and it has defines in place
for building on Windows; I was defining ACCESSPERMS
universally, but it should only be defined for non-Windows
systems, which the context in this code means Linux/BSD.

Signed-off-by: Leah Rowe <leah@libreboot.org>

musl libc is very conservative in what it implements,
preferring a very "pure" libc implementation. this means
that it lacks many of the niceties found in others like
the GNU C Library; the latter implements many BSD libc
extensions, for example.

ACCESSPERMS is a #define in BSD libc that does:
S_IRWXU | S_IRWXG | S_IRWXO

Essentially, it provides a bitwise OR providing chmod 0777,
which can be used as shorthand in calls to functions such
as mkdir() available in all libc implementations.

In the case of uefitool, this define is indeed used on mkdir.
Conditionally re-define ACCESSPERMS, if undefined, so that musl
libc can be used when building uefitool.

Signed-off-by: Leah Rowe <leah@libreboot.org>