kmsgrab: Only gain effective CAP_SYS_ADMIN when needed

cmake/FindLIBCAP.cmake

@@ -0,0 +1,21 @@
+# - Try to find Libcap
+# Once done this will define
+#
+#  LIBCAP_FOUND - system has Libcap
+#  LIBCAP_INCLUDE_DIRS - the Libcap include directory
+#  LIBCAP_LIBRARIES - the libraries needed to use Libcap
+#  LIBCAP_DEFINITIONS - Compiler switches required for using Libcap
+
+# Use pkg-config to get the directories and then use these values
+# in the find_path() and find_library() calls
+find_package(PkgConfig)
+pkg_check_modules(PC_LIBCAP libcap)
+
+set(LIBCAP_DEFINITIONS ${PC_LIBCAP_CFLAGS})
+
+find_path(LIBCAP_INCLUDE_DIRS sys/capability.h PATHS ${PC_LIBCAP_INCLUDEDIR} ${PC_LIBCAP_INCLUDE_DIRS})
+find_library(LIBCAP_LIBRARIES NAMES libcap.so PATHS ${PC_LIBCAP_LIBDIR} ${PC_LIBCAP_LIBRARY_DIRS})
+mark_as_advanced(LIBCAP_INCLUDE_DIRS LIBCAP_LIBRARIES)
+
+include(FindPackageHandleStandardArgs)
+find_package_handle_standard_args(LIBCAP REQUIRED_VARS LIBCAP_LIBRARIES LIBCAP_INCLUDE_DIRS)