Fix build on musl libc

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On util.c the guard around #include sys/sysmacros.h prevents musl libc from including the file, even though musl provides the header file, thus failing with errors such as "call to undeclared function makedev".

In procenv.c although the function makedev is used but the file sysmacros.h was never included, thus resulting in similar "call to undeclared function makedev" error hence moving inclusion sysmacros.h to source file from header file.