configure.ac: inputproto 2.4 is optional
Missing else condition in PKG_CHECK_MODULES caused configure to bail out where 2.4 wasn't available.
Found by @alexhorner in libinput/libinput!775 (comment 1678232)
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Missing else condition in PKG_CHECK_MODULES caused configure to bail out where 2.4 wasn't available.
Found by @alexhorner in libinput/libinput!775 (comment 1678232)