cmake: Add module to find libsysinfo on FreeBSD

Add cmake module to find the sysinfo compatibility library used on
FreeBSD to emulate that linux specific system call.

cmake/Modules/FindLibsysinfo.cmake

@@ -0,0 +1,24 @@
+# Once done these will be defined:
+#
+#  SYSINFO_FOUND
+#  SYSINFO_INCLUDE_DIRS
+#  SYSINFO_LIBRARIES
+
+find_path(SYSINFO_INCLUDE_DIR
+	NAMES sys/sysinfo.h
+	PATHS
+		/usr/include /usr/local/include /opt/local/include)
+
+find_library(SYSINFO_LIB
+	NAMES sysinfo libsysinfo
+	PATHS
+		/usr/lib /usr/local/lib /opt/local/lib)
+
+include(FindPackageHandleStandardArgs)
+find_package_handle_standard_args(sysinfo DEFAULT_MSG SYSINFO_LIB SYSINFO_INCLUDE_DIR)
+mark_as_advanced(SYSINFO_INCLUDE_DIR SYSINFO_LIB)
+
+if(SYSINFO_FOUND)
+	set(SYSINFO_INCLUDE_DIRS ${SYSINFO_INCLUDE_DIR})
+	set(SYSINFO_LIBRARIES ${SYSINFO_LIB})
+endif()