Warn about disabled schur specializations.

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CMakeLists.txt

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 7c1c19c..c00d8b9 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -242,6 +242,7 @@
   # Disable fixed-size specializations of the schur complement solver, which
   # requires multiple gigabytes of memory to compile.
   ADD_DEFINITIONS(-DCERES_RESTRICT_SCHUR_SPECIALIZATION)
+  MESSAGE("-- Disabling Schur specializations (faster compiles)")
 ENDIF (NOT SCHUR_SPECIALIZATIONS)
 
 OPTION(OPENMP