Change metis library detection

The Ubuntu packages do not ship with a pkg-config file. Change the
library detection to simply `find_library`.

CMakeLists.txt

@@ -151,11 +151,13 @@ list(APPEND LINK_LIBRARIES ${LAPACK_LIBRARIES} ${BLAS_LIBRARIES})
 
 set(PROGRESS_GRAPHLIB FALSE CACHE BOOL "Compile with externel graph libraries")
 if(PROGRESS_GRAPHLIB)
-  pkg_check_modules(METIS metis REQUIRED)
-  message(STATUS "Found metis: ${METIS_LDFLAGS}")
+  find_library(FOUND_METIS metis)
+  if(NOT FOUND_METIS)
+    message(FATAL_ERROR "Could not find metis library")
+  endif()
   message(STATUS "Will build with external graph libraries")
   add_definitions(-DDO_GRAPHLIB)
-  list(APPEND LINK_LIBRARIES ${METIS_LDFLAGS})
+  list(APPEND LINK_LIBRARIES -lmetis)
 endif()
 
 set(PROGRESS_OPENMP TRUE CACHE BOOL "Whether to compile with OpenMP support")