compiler.h: Do not include sys/io.h on ARM with glibc

Matt Turner requested to merge mattst88/xserver:for-1.20.6 into server-1.20-branch

<sys/io.h> on ARM hasn't worked for a long, long time, so it was removed it from glibc upstream.

Remove the include to avoid a compilation failure on ARM with glibc.

Signed-off-by: Olivier Fourdan Closes: #840 (closed) (cherry picked from commit fe4cd0e7)

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