this header is required when building the extended block device plugins
on linux, without it the build fails like:
```
/home/kefu/dev/ceph/src/extblkdev/ExtBlkDevInterface.h:38:10: fatal error: 'sys/capability.h' file not found
38 | #include <sys/capability.h>
| ^~~~~~~~~~~~~~~~~~
```
so, let's mark this package REQUIRED, so that we can fail early
when generating the building system.
Signed-off-by: Kefu Chai <tchaikov@gmail.com>
add_library(extblkdev STATIC ExtBlkDevPlugin.cc)
-if(NOT WIN32)
-find_package(cap)
-target_link_libraries(extblkdev cap)
+if(LINUX)
+ find_package(cap REQUIRED)
+ target_link_libraries(extblkdev cap)
endif()
add_custom_target(extblkdev_plugins DEPENDS