sane-backends: Fix for Linuxbrew
sane-backends: Fix for Linuxbrew

Only apply the Homebrew patch on macOS

Fix error:
sanei_ir.c:192:15: error: 'INT_MIN' undeclared (first use in this function)

Closes Linuxbrew/homebrew-core#871.

Signed-off-by: Bob W. Hogg <c772a964fd55352a3510e5d535dd9ccc9ac30168@linux.com>

rwhogg/homebrew-core,maxim-belkin/homebrew-core,Linuxbrew/homebrew-core,Linuxbrew/homebrew-core,maxim-belkin/homebrew-core,LinuxbrewTestBot/homebrew-core,rwhogg/homebrew-core,LinuxbrewTestBot/homebrew-core